FilterControlOperationVisibilityEventArgs.FunctionType Property

Gets a function-based comparison operator type.

Namespace: DevExpress.Web

Assembly: DevExpress.Web.v24.1.dll

NuGet Package: DevExpress.Web

Declaration

C#

public FunctionOperatorType FunctionType { get; }

VB.NET

Public ReadOnly Property FunctionType As FunctionOperatorType

Property Value

Type	Description
FunctionOperatorType	An enumeration value.

Available values:

Show 141 items

Name	Description
None	The function type is not specified.
Custom	Identifies a custom operation. This operation is executed on the client side if its operands are constants. A custom operation is executed on the server side only if its operands cannot be evaluated locally. For more information on how to implement custom operators, review the following help topic: How to: Implement a Custom Criteria Language Function Operator. The eXpress Persistent Objects framework provides two custom function operators - IsExactTypeFunction and IsInstanceOfTypeFunction.
CustomNonDeterministic	Identifies a custom nondeterministic operation. Unlike a standard custom operation, a custom nondeterministic operation is always executed on the server side, regardless of whether its operands are constants. For more information on how to implement custom operators, review the following help topic: How to: Implement a Custom Criteria Language Function Operator.
Iif	Returns one of the specified values depending upon the values of logical expressions. The function can take 2N+1 arguments (where N is the number of specified logical expressions): Each odd argument specifies a logical expression. Each even argument specifies the value that is returned if the previous expression evaluates to True. The last argument specifies the value that is returned if the previously evaluated logical expressions yield False. If you pass only one argument, the passed argument is returned. If you compare a 0 (zero) with a Null value, the expression evaluates to True. Examples: Iif(Name = 'Bob', 1, 0) Iif(Name = 'Bob', 1, Name = 'Dan', 2, Name = 'Sam', 3, 0)
IsNull	Compares the first operand with the NULL value. This function requires one or two operands of the CriteriaOperator class. The returned value depends on the number of arguments. If a single operand is passed, the function returns True if the operand is null; otherwise, False. If two operands are passed, the function returns the second operand if the first operand is null. Otherwise, the function returns the first operand.
IsNullOrEmpty	Returns True if the specified value is null or an empty string. Otherwise, returns False.
Trim	Returns a string that is a copy of the specified string with all white-space characters removed from the start and end of the specified string.
Len	Returns the length of the string specified by an operand. To create the Len operator using the CriteriaOperator.Parse method, use the following syntax: CriteriaOperator.Parse("Len(Field1)").
Substring	Returns a substring from the specified string. This function requires two or three operands. If two operands are passed, the substring starts from the beginning of the specified string. The operands are: 1 - the source string. 2 - an integer that specifies the zero-based position at which the substring starts. If three operands are passed, a substring starts from the specified position in the source string. The operands are: 1 - the source string. 2 - an integer that specifies the zero-based position at which the substring starts. 3 - an integer that specifies the length of the substring.
Upper	Converts all characters in a string operand to uppercase in an invariant culture.
Lower	Converts all characters in a string operand to lowercase in an invariant culture.
Concat	Concatenates the specified strings.
Ascii	Returns the ASCII code of the first character in a string operand. If the argument is an empty string, the null value is returned.
Char	Converts a numeric operand to a Unicode character. If the specified operand is not numeric, the NotSupportedException is thrown.
ToStr	Returns a string representation of the specified value or property. If the operand cannot be converted to a string, the NotSupportedException is thrown.
Replace	Returns a new string in which all occurrences of one specified string (string1) in another string (string2) are replaced with the specified string (string3). The operands are: 1 - the string in which replacements are made. 2 - the string to be replaced. 3 - the string to replace all occurrences of the specified string.
Reverse	Returns a string in which the character order of a specified string is reversed.
Insert	Returns a new string in which a specified string is inserted at a specified index position into another specified string. The operands are: 1 - the string into which another string should be inserted. 2 - the zero-based index position of the insertion. 3 - the string to insert.
CharIndex	Returns the index of the first occurrence of a specified string within another string. The operands are: 1 - a string that you want to find in another string. 2 - a string that contains the string you are searching for. 3 - (optional) an integer that specifies the zero-based index at which the search starts. If this operand is not specified, the search begins from the start of the string. 4 - (optional) an integer that specifies the number of characters to examine, starting from the specified position. If this operand is not specified, the search continues until the end of the string. This function performs a word (case-sensitive and culture-sensitive) search using the current culture. If a specified substring is found, the function returns its index. Otherwise, -1 is returned.
Remove	Returns a new string with the specified number of characters in the specified string removed, starting at the specified position. The operands are: 1 - the string that needs to be shortened. 2 - the zero-based index at which character removal starts. 3 - (optional) an integer that specifies the number of characters to remove, starting at the specified position. If this operand is not specified, all characters between the starting position and the end of the string are removed.
Abs	Returns the absolute value of a numeric operand. If the operand is not numeric, the NotSupportedException is thrown.
Sqr	Returns the square root of a specified numeric operand. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Cos	Returns the cosine of the numeric operand, in radians. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Sin	Returns the sine of the numeric operand, in radians. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Atn	Returns the arctangent (the inverse tangent function) of the numeric operand. The arctangent is the angle in the range -π/2 to π/2 radians, whose tangent is the numeric operand. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Exp	Returns the number e raised to the power specified by a numeric operand. If the specified operand cannot be converted to Double, the NotSupportedException is thrown. The Exp function reverses the FunctionOperatorType.Log function. Use the FunctionOperatorType.Power operand to calculate powers of other bases.
Log	Returns the logarithm of the specified numeric operand. The return value depends upon the number of operands. If one operand is passed, the function returns the natural (base e) logarithm of a specified operand. If two operands are passed, the function returns the logarithm of the specified operand to the specified base. The operands are: 1 - a number whose logarithm is to be calculated. 2 - the base of the logarithm. If the operand cannot be converted to Double, the NotSupportedException is thrown. The Log function reverses the FunctionOperatorType.Exp function. To calculate the base-10 logarithm, use the FunctionOperatorType.Log10 function.
Rnd	Returns a random number greater than or equal to 0.0, and less than 1.0.
Tan	Returns the tangent of the specified numeric operand that is an angle in radians. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Power	Returns a specified numeric operand raised to a specified power. The operands are: 1 - the base number. 2 - the exponent to which the base number is raised. If the operand cannot be converted to Double, the NotSupportedException is thrown. The Power function reverses the FunctionOperatorType.Log or FunctionOperatorType.Log10 function. Use the FunctionOperatorType.Exp operand to calculate powers of the number e.
Sign	Returns an integer that indicates the sign of a number. The function returns 1 for positive numbers, -1 for negative numbers, and 0 (zero) if a number is equal to zero. If a specified operand is not numeric, the NotSupportedException is thrown.
Round	Rounds a specified numeric operand to the nearest integer or to a specified number of fractional digits. The operands are: 1 - a value to round. 2 - (optional) the number of decimal places to which to round. 0 indicates that the first operand is rounded to the nearest integer.
Ceiling	Returns the smallest integral value greater than or equal to the specified numeric operand. If the specified operand is not numeric, the NotSupportedException is thrown.
Floor	Returns the largest integral value less than or equal to the specified numeric operand. If the specified operand is not numeric, the NotSupportedException is thrown.
Max	Returns the larger of two numeric values.
Min	Returns the smaller of two numeric values.
Acos	Returns the arccosine of the numeric operand. The arccosine is the angle in the range 0 (zero) to π radians, whose cosine is the numeric operand. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Asin	Returns the arcsine of the numeric operand. The arcsine is the angle in the range -π/2 to π/2 radians, whose sine is the numeric operand. If the specified operand cannot be converted to Double, the NotSupportedException is thrown.
Atn2	Returns the arctangent (the inverse tangent function) of the quotient of the two specified numeric operands. The arctangent is the angle in the range -π/2 to π/2 radians. The operands are: 1 - the y coordinate of a point in Cartesian coordinates (x, y). 2 - the x coordinate of a point in Cartesian coordinates (x, y). If the specified operands cannot be converted to Double, the NotSupportedException is thrown.
BigMul	Calculates the full product of two integer operands. If the specified operands cannot be converted to Int32, the NotSupportedException is thrown.
Cosh	Returns the hyperbolic cosine of the numeric operand, in radians. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Log10	Returns the base 10 logarithm of the specified numeric operand. If the operand cannot be converted to Double, the NotSupportedException is thrown. The Log10 function reverses the FunctionOperatorType.Power function. Use the FunctionOperatorType.Log operand to calculate the logarithm of other bases.
Sinh	Returns the hyperbolic sine of the numeric operand, in radians. If the operand cannot be converted to Double, the NotSupportedException is thrown.
Tanh	Returns the hyperbolic tangent of a specified numeric operand that is an angle in radians. If the specified operands cannot be converted to Double, the NotSupportedException is thrown.
PadLeft	Returns a new string that pads the character in the specified string on the left with a specified Unicode character, for a specified total length. The operands are: 1 - a string to be padded. 2 - the total number of characters in the resulting string, including padding characters. 3 - (optional) a Unicode padding character. If not specified, the space character is used for padding. If a string is passed as this operand, its first character is used for padding.
PadRight	Returns a new string of a specified length in which the end of a specified string is padded with spaces or with a specified Unicode character. The operands are: 1 - a string to be padded. 2 - the total number of characters in the resulting string, including padding characters. 3 - (optional) a Unicode padding character. If not specified, the space character is used for padding. If a string is passed as this operand, its first character is used for padding.
StartsWith	Returns True if the beginning of one string matches another string; otherwise, False. The operands are: 1 - a string to test. 2 - a string to match the beginning of another string.
EndsWith	Returns True if the end of one specified string matches another specified string; otherwise, False. The operands are: 1 - a string that contains the string you are searching for. 2 - a string to compare to the substring at the end of another string. To create the EndsWith operator using the CriteriaOperator.Parse method, use the following syntax: CriteriaOperator.Parse("EndsWith(String, SubString)").
Contains	Returns True if the specified string occurs within another specified string; otherwise, False. The operands are: 1 - a string that contains the string you are searching for. 2 - a string that you want to find in another string.
ToInt	Converts a numeric operand to an integer value.
ToLong	Converts a numeric operand to a long integer value.
ToFloat	Converts a numeric operand to a floating-point value.
ToDouble	Converts a numeric operand to a double value.
ToDecimal	Converts a numeric operand to a decimal value.
LocalDateTimeThisYear	Returns the DateTime value with the date part that is the first day of the current year, and the time part of 00:00:00.
LocalDateTimeThisMonth	Returns the DateTime value with the date part that is the first day of the current month, and the time part of 00:00:00.
LocalDateTimeLastWeek	Returns the DateTime value that has the date part that is 7 days before the start of the current week, and the time part of 00:00:00.
LocalDateTimeThisWeek	Returns the DateTime value with the date part that is the first day of the current week, and the time part of 00:00:00.
LocalDateTimeYesterday	Returns the DateTime value with the date part that is the previous day, and the time part of 00:00:00.
LocalDateTimeToday	Returns the DateTime value with the date part that is the start of the current day, and the time part of 00:00:00.
LocalDateTimeNow	Returns the DateTime value that is the current moment in time.
LocalDateTimeTomorrow	Returns the DateTime value with the date part that is the next day, and the time part of 00:00:00.
LocalDateTimeDayAfterTomorrow	Returns the DateTime value that has the date part that is two days after the current date, and the time part of 00:00:00.
LocalDateTimeNextWeek	Returns the DateTime value that has the date part that is 7 days after the start of the current week, and the time part of 00:00:00.
LocalDateTimeTwoWeeksAway	Returns the DateTime value with the date part that is the first day of the week after the next week, and the time part of 00:00:00.
LocalDateTimeNextMonth	Returns the DateTime value that has the date part that is the first day of the next month, and the time part of 00:00:00.
LocalDateTimeNextYear	Returns the DateTime value with the date part that corresponds to the first day of the next year, and the time part of 00:00:00.
LocalDateTimeTwoMonthsAway	Returns the DateTime value with the date part that is the first day of the month after the next month, and the time part of 00:00:00.
LocalDateTimeTwoYearsAway	Returns the DateTime value with the date part that is the first day of the year after the next year, and the time part of 00:00:00.
LocalDateTimeLastMonth	Returns the DateTime value that has the date part that is one month before the current date, and the time part of 00:00:00.
LocalDateTimeLastYear	Returns the DateTime value that has the date part that is the first day of the previous year, and the time part of 00:00:00.
LocalDateTimeYearBeforeToday	Returns the DateTime value with the date part that is the date one year ago, and the time part of 00:00:00.
IsOutlookIntervalBeyondThisYear	The Boolean Is Beyond This Year operator for date/time values. Requires one argument. The operator is defined as follows: date >= First Day of Next Year
IsOutlookIntervalLaterThisYear	The Boolean Is Later This Year operator for date/time values. Requires one argument. The operator is defined as follows: First Day of Next Month <= date < First Day of Next Year
IsOutlookIntervalLaterThisMonth	The Boolean Is Later This Month operator for date/time values. Requires one argument. The operator is defined as follows: Last Day of Next Week < date < First Day of Next Month
IsOutlookIntervalNextWeek	The Boolean Is Next Week operator for date/time values. Requires one argument. The operator is defined as follows: First Day of Next Week <= date <= Last Day of Next Week
IsOutlookIntervalLaterThisWeek	The Boolean Is Later This Week operator for date/time values. Requires one argument. The operator is defined as follows: Day After Tomorrow <= date < First Day of Next Week
IsOutlookIntervalTomorrow	The Boolean Is Tomorrow operator for date/time values. Requires one argument.
IsOutlookIntervalToday	The Boolean Is Today operator for date/time values. Requires one argument.
IsOutlookIntervalYesterday	The Boolean Is Yesterday operator for date/time values. Requires one argument.
IsOutlookIntervalEarlierThisWeek	The Boolean Is Earlier This Week operator for date/time values. Requires one argument. The operator is defined as follows: First Day of This Week <= date < Yesterday
IsOutlookIntervalLastWeek	The Boolean Is Last Week operator for date/time values. Requires one argument. The operator is defined as follows: First Day of Last Week <= date < First Day of This Week
IsOutlookIntervalEarlierThisMonth	The Boolean Is Earlier This Month operator for date/time values. Requires one argument. The operator is defined as follows: First Day of This Month <= date < First Day of Last Week
IsOutlookIntervalEarlierThisYear	The Boolean Is Earlier This Year operator for date/time values. Requires one argument. The operator is defined as follows: First Day of This Year <= date < First Day of This Month
IsOutlookIntervalPriorThisYear	The Boolean Is Prior This Year operator for date/time values. Requires one argument. The operator is defined as follows: date < First Day of This Year
IsThisWeek	Returns True if the specified date falls within the current week.
IsThisMonth	Returns True if the specified date falls within the current month. To create the IsThisMonth operator using the CriteriaOperator.Parse method, use the following syntax: CriteriaOperator.Parse(“IsThisMonth(StartDate)”).
IsThisYear	Returns True if the specified date falls within the current year.
IsNextMonth	Returns True if the specified date falls within the next month.
IsNextYear	Returns True if the specified date falls within the next year.
IsLastMonth	Returns True if the specified date falls within the previous month.
IsLastYear	Returns True if the specified date falls within the previous year.
IsYearToDate	Returns True if the specified date falls within the period that starts from the first day of the current year and continues until the current date (including the current date).
IsSameDay	Returns True if the specified date/time value falls within the same day. To create the IsSameDay operator using the CriteriaOperator.Parse method, use the following syntax: CriteriaOperator.Parse(“IsSameDay(StartDate)”).
InRange	Returns True if the first operand is greater than or equal to the second operand and less than or equal to the third operand. Otherwise, returns False. If operands cannot be compared, returns null. The operands are: 1 - the DateTime value that is the value to test. 2 - the DateTime value that is the minimum value. 3 - the DateTime value that is the maximum value.
InDateRange	Returns True if the date part of the first operand is greater than or equal to the date part of the second operand and less than or equal to the date part of the third operand. Otherwise, returns False. If operands cannot be compared, returns null. The operands are: 1 - the DateTime/DateOnly value that is the date to test. 2 - the DateTime/DateOnly value that is the start date. 3 - the DateTime/DateOnly value that is the end date.
IsJanuary	Returns True if the specified date falls within January.
IsFebruary	Returns True if the specified date falls within February.
IsMarch	Returns True if the specified date falls within March.
IsApril	Returns True if the specified date falls within April.
IsMay	Returns True if the specified date falls within May.
IsJune	Returns True if the specified date falls within June.
IsJuly	Returns True if the specified date falls within July.
IsAugust	Returns True if the specified date falls within August.
IsSeptember	Returns True if the specified date falls within September.
IsOctober	Returns True if the specified date falls within October.
IsNovember	Returns True if the specified date falls within November.
IsDecember	Returns True if the specified date falls within December.
DateDiffTick	Returns the number of tick boundaries between the specified dates. The operands are: 1 - the DateTime value that is the start date. 2 - the DateTime value that is the end date.
DateDiffSecond	Returns the number of second boundaries between the specified dates/times. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the DateTime/TimeOnly value that is the end date.
DateDiffMilliSecond	Returns the number of millisecond boundaries between the specified dates/times. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the DateTime/TimeOnly value that is the end date.
DateDiffMinute	Returns the number of minute boundaries between the specified dates/times. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the DateTime/TimeOnly value that is the end date.
DateDiffHour	Returns the number of hour boundaries between the specified dates/times. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the DateTime/TimeOnly value that is the end date.
DateDiffDay	Returns the number of day boundaries between the specified dates. The operands are: 1 - the DateTime/DateOnly value that is the start date. 2 - the DateTime/DateOnly value that is the end date.
DateDiffMonth	Returns the number of month boundaries between the specified dates. The operands are: 1 - the DateTime/DateOnly value that is the start date. 2 - the DateTime/DateOnly value that is the end date.
DateDiffYear	Returns the number of year boundaries between the specified dates. The operands are: 1 - the DateTime/DateOnly value that is the start date. 2 - the DateTime/DateOnly value that is the end date.
GetDate	Returns the date part of the specified date. The operand must be of the DateTime type. The return value is a DateTime object with the same date part. The time part is 00:00:00.
GetMilliSecond	Returns the milliseconds value in the specified date/time. The operand must be of the DateTime/TimeOnly type. The return value is an integer in the range between 0 and 999.
GetSecond	Returns the seconds value in the specified date/time. The operand must be of the DateTime/TimeOnly type. The return value is an integer in the range between 0 and 59.
GetMinute	Returns the minutes value in the specified date/time. The operand must be of the DateTime/TimeOnly type. The return value is an integer in the range between 0 and 59.
GetHour	Returns the hours value in the specified date/time. The operand must be of the DateTime/TimeOnly type. The return value is an integer in the range between 0 and 23.
GetDay	Gets the day of the month in the specified date. The operand must be of the DateTime/DateOnly type. The return value is an integer in the range between 1 and 31.
GetMonth	Gets the month in the specified date. The operand must be of the DateTime/DateOnly type. The return value is an integer and depends on the current calendar.
GetYear	Gets the year in the specified date. The operand must be of the DateTime/DateOnly type. The return value is an integer in the range between 1 and 9999.
GetDayOfWeek	Gets the day of the week in the specified date. The operand must be of the DateTime/DateOnly type. The return value is an integer value of the DayOfWeek enumeration. It does not depend on the current culture.
GetDayOfYear	Gets the day of the year in the specified date. The operand must be of the DateTime/DateOnly type. The return value is an integer in the range between 1 and 366.
GetTimeOfDay	Gets the time part of the specified date. The operand must be of the DateTime type. The return value is the Int64 object that is the number of 100-nanosecond ticks that have elapsed since midnight.
Now	Returns the DateTime value that is the current date and time.
UtcNow	Returns a DateTime object that is the current date and time in Universal Coordinated Time (UTC).
Today	Returns a DateTime value that is the current date. The time part is set to 00:00:00.
AddTimeSpan	Returns a DateTime value that differs by a specified amount of time from a specified date. The operands are: 1 - the DateTime value that is the start date. 2 - the TimeSpan object that is the time period before or after the start date.
AddTicks	Returns a DateTime value that is the specified number of ticks before or after a specified start date. The operands are: 1 - the DateTime value that is the start date. 2 - the integer number that is the number of 100-nanosecond ticks. This number can be negative or positive.
AddMilliSeconds	Returns a DateTime/TimeOnly value that is the specified number of milliseconds before or after a specified start date/time. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the Double value that is the number of milliseconds before or after the start date. This number can be negative or positive. Its decimal part is a fraction of a millisecond.
AddSeconds	Returns a DateTime/TimeOnly value that is the specified number of seconds before or after a specified start date/time. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the Double value that is the number of seconds before or after the start date. This number can be negative or positive. Its decimal part is a fraction of a second.
AddMinutes	Returns a DateTime/TimeOnly value that is the specified number of minutes before or after a specified start date/time. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the Double value that is the number of minutes before or after the start date. This number can be negative or positive. Its decimal part is a fraction of a minute.
AddHours	Returns a DateTime/TimeOnly value that is the specified number of hours before or after a specified start date/time. The operands are: 1 - the DateTime/TimeOnly value that is the start date. 2 - the Double value that is the number of hours before or after the start date. This number can be negative or positive. Its decimal part is a fraction of an hour.
AddDays	Returns a DateTime/DateOnly value that is the specified number of days before or after a specified start date. The operands are: 1 - the DateTime/DateOnly value that is the start date. 2 - the Double value that is the number of days before or after the start date. This number can be negative or positive. Its decimal part is a fraction of a day.
AddMonths	Returns a DateTime/DateOnly value that is the specified number of months before or after a specified start date. The operands are: 1 - the DateTime/DateOnly value that is the start date. 2 - the integer value that is the number of months before or after the start date. This number can be negative or positive.
AddYears	Returns a DateTime/DateOnly value that is the specified number of years before or after a specified start date. The operands are: 1 - the DateTime/DateOnly value that is the start date. 2 - the integer value that is the number of years before or after the start date. This number can be negative or positive.
DateTimeFromParts	Returns a date value constructed from the specified Year, Month, Day, Hour, Minute, Second, and Millisecond. The operands are: 1 - (Required) - an integer value that is the full year value (four digits, century included). 2 - (Required) - an integer value that is the month number (1-12). 3 - (Required) - an integer value that is the day of the month (1-31). 4 - (Optional) - an hour value in 24-hour format (0-23). 5 - (Optional) - a minute value (0-59). 6 - (Optional) - a second value (0-59). 7 - (Optional) - a millisecond value.
DateOnlyFromParts	Returns a DateOnly value constructed from the specified Year, Month, and Day. The operands are: 1 - an integer value that is the full year value (four digits, century included). 2 - an integer value that is the month number (1-12). 3 - an integer value that is the day of the month (1-31).

Remarks

Filter expressions support predefined and custom function-based comparison operators. To get a function-based operator type, use the FunctionType property. If the FunctionOperatorType enumeration does not contain the current operator type, the FunctionType property value is None.

For a function-based operator, the Operation property gets the Function value.

The example below demonstrates how to process FunctionType property values to keep only the “Is January” and “Is February” operators visible.

ASPX

<dx:ASPxFilterControl ID="filter" runat="server" 
    OnOperationVisibility="filter_OperationVisibility">
    <Columns>
        <dx:FilterControlColumn PropertyName="Date" ColumnType="DateTime" />
        <!--...-->
    </Columns>
</dx:ASPxFilterControl>

C#

using DevExpress.Web;
using DevExpress.Data.Filtering;
using DevExpress.Data.Filtering.Helpers;

protected void filter_OperationVisibility(object sender, FilterControlOperationVisibilityEventArgs e)
{
    if (!(e.Operation == ClauseType.Function &&
         (e.FunctionType == FunctionOperatorType.IsJanuary || 
          e.FunctionType == FunctionOperatorType.IsFebruary))) {
        e.Visible = false;
    }
}

VB.NET

Imports DevExpress.Web
Imports DevExpress.Data.Filtering
Imports DevExpress.Data.Filtering.Helpers

Protected Sub filter_OperationVisibility(ByVal sender As Object, ByVal e As FilterControlOperationVisibilityEventArgs)
    If Not(e.Operation = ClauseType.Function AndAlso _
          (e.FunctionType = FunctionOperatorType.IsJanuary OrElse _
           e.FunctionType = FunctionOperatorType.IsFebruary)) Then
        e.Visible = False
    End If
End Sub

Supported Function-Based Operators

A filter control supports any operator type from the FunctionOperatorType enumeration to specify a filter expression in the Text tab or in code.

In the Visual tab, the control displays function-based operators of the following types:

• IsSameDay
• IsThisMonth
• IsThisWeek
• IsThisYear
• IsNextMonth
• IsNextYear
• IsLastMonth
• IsLastYear
• IsYearToDate
• IsJanuary
• IsFebruary
• IsMarch
• IsApril
• IsMay
• IsJune
• IsJuly
• IsAugust
• IsSeptember
• IsOctober
• IsNovember
• IsDecember