Session.GetObjectsFromQueryAsync<T>(List<XPMemberInfo>, String, QueryParameterCollection, CancellationToken) Method

Asynchronously executes a SQL query and returns its result set as a collection of non-persistent objects.

Namespace: DevExpress.Xpo

Assembly: DevExpress.Xpo.v24.1.dll

NuGet Packages: DevExpress.Win.PivotGrid, DevExpress.Win.TreeMap, DevExpress.Xpo

NuGet Package: DevExpress.Xpo

Declaration

C#

public Task<ICollection<T>> GetObjectsFromQueryAsync<T>(
    List<XPMemberInfo> members,
    string sql,
    QueryParameterCollection parameters,
    CancellationToken cancellationToken = default(CancellationToken)
)

VB.NET

Public Function GetObjectsFromQueryAsync(Of T)(
    members As List(Of XPMemberInfo),
    sql As String,
    parameters As QueryParameterCollection,
    cancellationToken As CancellationToken = Nothing
) As Task(Of ICollection(Of T))

Parameters

Name	Type	Description
members	List<XPMemberInfo>	Specifies object members mapped to columns in the result set. The order of list elements should correspond to the order of result set columns.
sql	String	Specifies an SQL statement.
parameters	QueryParameterCollection	Specifies query parameter values.

Optional Parameters

Name	Type	Default	Description
cancellationToken	CancellationToken	null	A CancellationToken object that delivers a cancellation notice to the running operation.

Type Parameters

Name	Description
T	The type of objects returned by the method. A class that implements this type sould be decorated with NonPersistentAttribute.

Returns

Type	Description
Task<ICollection<T>>	A Task<TResult> that returns a collection of non-persistent classInfo objects instantiated with data obtained via the specified SQL query.

Remarks

Use QueryParameterCollection to pass strongly-typed parameters. See examples here: Always Encrypted (SQL Server only).

C#

string sql = "select (FirstName + ' ' + LastName) as Name, City, Country from Employees where City = @p0";
XPClassInfo classInfo = session.GetClassInfo<EmployeeModel>();
List<XPMemberInfo> members = new List<XPMemberInfo>() {
    classInfo.GetMember(nameof(EmployeeModel.Name)),
    classInfo.GetMember(nameof(EmployeeModel.City)),
    classInfo.GetMember(nameof(EmployeeModel.Country))
};
QueryParameterCollection parameters = new QueryParameterCollection() {
    new ParameterValue() { DBTypeName = "nvarchar(15)", Value = "London" }
};
ICollection<EmployeeModel> queryResultData = await session.GetObjectsFromQueryAsync<EmployeeModel>(members, sql, parameters);

VB.NET

Dim sql As String = "select (FirstName + ' ' + LastName) as Name, City, Country from Employees where City = @p0"
Dim classInfo As XPClassInfo = session.GetClassInfo(Of EmployeeModel)()
Dim members As New List(Of XPMemberInfo)() From { _
    classInfo.GetMember(nameof(EmployeeModel.Name)), _
    classInfo.GetMember(nameof(EmployeeModel.City)), _
    classInfo.GetMember(nameof(EmployeeModel.Country)) _
}
Dim parameters As New QueryParameterCollection() From {
    New ParameterValue() With {.DBTypeName = "nvarchar(15)", .Value = "London"}
}
Dim queryResultData As ICollection(Of EmployeeModel) = Await session.GetObjectsFromQueryAsync(Of EmployeeModel)(members, sql, parameters)

The connection provider automatically generates sequential parameter names (p0, p1, p2 …). To specify custom parameter names, use the overloaded GetObjectsFromQueryAsync<T>(List<XPMemberInfo>, String, String[], QueryParameterCollection, CancellationToken) method.

This method does the following:

• Executes the specified SQL query and obtains the query result.
• Creates objects of the specified type and populates their properties with the resulting set’s data. The members parameter specifies the mapping between columns in the resulting set and object properties. Note that the GetObjectsFromQuery<T> method’s generic type parameter should specify a non-persistent class decorated with a NonPersistentAttribute.
• Populates a collection with these objects.

Note

The GetObjectsFromQueryAsync<T> method throws an exception if the members list includes any of the following object members:

• A property that is not defined within the T type.
• A struct type member.
• A reference to a class with a struct type member.
• A collection used in object relations.

To learn more about executing SQL statements in XPO, refer to Direct SQL Queries.

Note

The GetObjectsFromQueryAsync method sends statements directly, so the correct statement syntax and parameter names format depends on a particular database server.