ColumnView.CustomDrawEmptyForeground Event

Enables a View’s empty space to be custom painted when there aren’t any rows displayed.

Namespace: DevExpress.XtraGrid.Views.Base

Assembly: DevExpress.XtraGrid.v24.2.dll

Declaration

C#

[DXCategory("CustomDraw")]
public event CustomDrawEventHandler CustomDrawEmptyForeground

VB.NET

<DXCategory("CustomDraw")>
Public Event CustomDrawEmptyForeground As CustomDrawEventHandler

Event Data

The CustomDrawEmptyForeground event's data class is CustomDrawEventArgs. The following properties provide information specific to this event:

Property	Description
Appearance	Gets the painted element’s appearance settings.
Bounds	Returns a value specifying limits for the drawing area.
Cache	Provides methods to paint on drawing surfaces in GDI+ and DirectX modes. See DirectX hardware acceleration to learn more.
Graphics	A GDI+ drawing surface. Use the CustomDrawEventArgs.Cache property instead if you enable the DirectX hardware acceleration.
Handled	Gets or sets a value specifying whether an event was handled and that the default element painting is therefore not required.

The event data class exposes the following methods:

Method	Description
DefaultDraw()	Performs default painting of an element.
DrawHtml(HtmlTemplate, DxHtmlPainterContext, Action<DxHtmlPainterArgs>)	Paints the required HTML template inside an element that raised this event. The context parameter allows you to assign an object that transfers mouse events to template elements.
DrawHtml(HtmlTemplate, Action<DxHtmlPainterArgs>)	Paints the required HTML template inside an element that raised this event.

Remarks

The CustomDrawEmptyForeground event is raised before a View is painted assuming that there aren’t any rows displayed. This can occur if the bound data source is empty or none of the rows meet the specified filter condition. Note that this event fires for the GridControl.MainView only. The height of the detail View depends upon the number of records displayed, it’s adjusted so that empty space is never displayed.

Handle the CustomDrawEmptyForeground event to custom paint the View’s empty area. Custom painting this area can be useful to display explanatory messages so that end-users aren’t confused when there aren’t any records displayed.

You don’t necessarily need to paint the empty space background when handling the CustomDrawEmtpyForeground event. By default, the background color of this area is specified using the GridViewAppearances.Empty object. Handling the CustomDrawEmptyForeground event does not erase the default painted background unless you fill the background manually.

See the Custom Painting Basics and Custom Painting Scenarios topics for information on using custom draw events.

Important

Do not change cell values, modify the control’s layout, or change the control’s object model in the events used for custom control painting. Actions that update the layout can cause the control to malfunction.

Example

The code below employs the ColumnView.CustomDrawEmptyForeground event to draw a custom string within the Data Grid control area when the Grid has no records to display. Clicking the “Try Searching Again” link displays a dialog that allows end-users to modify the currently applied filter.

C#

private void Form3_Load1(object sender, EventArgs e) {
    CustomDrawEmptyForeground(gridControl1, gridView1);
}

public static void CustomDrawEmptyForeground(GridControl gridControl, GridView gridView) {
    string searchName = string.Empty;
    gridView.ActiveFilterCriteria = new BinaryOperator("Category_Name", searchName);

    // Initialize variables used to paint View's empty space in a custom manner
    Font noMatchesFoundTextFont = new Font("Tahoma", 10);
    Font trySearchingAgainTextFont = new Font("Tahoma", 15, FontStyle.Underline);
    Font trySearchingAgainTextFontBold = new Font(trySearchingAgainTextFont, FontStyle.Underline | FontStyle.Bold);
    SolidBrush linkBrush = new SolidBrush(DevExpress.Skins.EditorsSkins.GetSkin(DevExpress.LookAndFeel.UserLookAndFeel.Default.ActiveLookAndFeel).Colors["HyperLinkTextColor"]);
    string noMatchesFoundText = "No matches found";
    string trySearchingAgainText = "Try searching again";
    Rectangle noMatchesFoundBounds = Rectangle.Empty;
    Rectangle trySearchingAgainBounds = Rectangle.Empty;
    bool trySearchingAgainBoundsContainCursor = false;
    int offset = 10;

    //Handle this event to paint View's empty space in a custom manner
    gridView.CustomDrawEmptyForeground += (s, e) => {
        e.DefaultDraw();
        e.Appearance.Options.UseFont = true;
        e.Appearance.Font = noMatchesFoundTextFont;
        //Draw the noMatchesFoundText string
        Size size = e.Appearance.CalcTextSize(e.Cache, noMatchesFoundText, e.Bounds.Width).ToSize();
        int x = (e.Bounds.Width - size.Width) / 2;
        int y = e.Bounds.Y + offset;
        noMatchesFoundBounds = new Rectangle(new Point(x, y), size);
        e.Appearance.DrawString(e.Cache, noMatchesFoundText, noMatchesFoundBounds);
        //Draw the trySearchingAgain link
        e.Appearance.Font = trySearchingAgainBoundsContainCursor ? trySearchingAgainTextFontBold : trySearchingAgainTextFont;
        size = e.Appearance.CalcTextSize(e.Cache, trySearchingAgainText, e.Bounds.Width).ToSize();
        x = noMatchesFoundBounds.X - (size.Width - noMatchesFoundBounds.Width) / 2;
        y = noMatchesFoundBounds.Bottom + offset;
        size.Width += offset;
        trySearchingAgainBounds = new Rectangle(new Point(x, y), size);
        e.Appearance.DrawString(e.Cache, trySearchingAgainText, trySearchingAgainBounds, linkBrush);
    };

    gridView.MouseMove += (s, e) => {
        trySearchingAgainBoundsContainCursor = trySearchingAgainBounds.Contains(e.Location);
        gridControl.Cursor = trySearchingAgainBoundsContainCursor ? Cursors.Hand : Cursors.Default;
        gridView.InvalidateRect(trySearchingAgainBounds);
    };

    gridView.MouseDown += (s, e) => {
        if (trySearchingAgainBoundsContainCursor) {
            searchName = XtraInputBox.Show(string.Format("Enter {0}", "Name"), string.Format("Enter {0} dialog", "Name"), searchName);
            gridView.ActiveFilterCriteria = new DevExpress.Data.Filtering.BinaryOperator("Category_Name", searchName);
        }
    };
}

VB.NET

Private Sub Form3_Load1(ByVal sender As Object, ByVal e As EventArgs)
    CustomDrawEmptyForeground(gridControl1, gridView1)
End Sub

Public Shared Sub CustomDrawEmptyForeground(ByVal gridControl As GridControl, ByVal gridView As GridView)
    Dim searchName As String = String.Empty
    gridView.ActiveFilterCriteria = New BinaryOperator("Category_Name", searchName)

    ' Initialize variables used to paint View's empty space in a custom manner
    Dim noMatchesFoundTextFont As New Font("Tahoma", 10)
    Dim trySearchingAgainTextFont As New Font("Tahoma", 15, FontStyle.Underline)
    Dim trySearchingAgainTextFontBold As New Font(trySearchingAgainTextFont, FontStyle.Underline Or FontStyle.Bold)
    Dim linkBrush As New SolidBrush(DevExpress.Skins.EditorsSkins.GetSkin(DevExpress.LookAndFeel.UserLookAndFeel.Default.ActiveLookAndFeel).Colors("HyperLinkTextColor"))
    Dim noMatchesFoundText As String = "No matches found"
    Dim trySearchingAgainText As String = "Try searching again"
    Dim noMatchesFoundBounds As Rectangle = Rectangle.Empty
    Dim trySearchingAgainBounds As Rectangle = Rectangle.Empty
    Dim trySearchingAgainBoundsContainCursor As Boolean = False
    Dim offset As Integer = 10

    'Handle this event to paint View's empty space in a custom manner
    AddHandler gridView.CustomDrawEmptyForeground, Sub(s, e)
        e.DefaultDraw()
        e.Appearance.Options.UseFont = True
        e.Appearance.Font = noMatchesFoundTextFont
        'Draw the noMatchesFoundText string
        Dim size As Size = e.Appearance.CalcTextSize(e.Cache, noMatchesFoundText, e.Bounds.Width).ToSize()
        Dim x As Integer = (e.Bounds.Width - size.Width) \ 2
        Dim y As Integer = e.Bounds.Y + offset
        noMatchesFoundBounds = New Rectangle(New Point(x, y), size)
        e.Appearance.DrawString(e.Cache, noMatchesFoundText, noMatchesFoundBounds)
        'Draw the trySearchingAgain link
        e.Appearance.Font = If(trySearchingAgainBoundsContainCursor, trySearchingAgainTextFontBold, trySearchingAgainTextFont)
        size = e.Appearance.CalcTextSize(e.Cache, trySearchingAgainText, e.Bounds.Width).ToSize()
        x = noMatchesFoundBounds.X - (size.Width - noMatchesFoundBounds.Width) \ 2
        y = noMatchesFoundBounds.Bottom + offset
        size.Width += offset
        trySearchingAgainBounds = New Rectangle(New Point(x, y), size)
        e.Appearance.DrawString(e.Cache, trySearchingAgainText, trySearchingAgainBounds, linkBrush)
    End Sub

    AddHandler gridView.MouseMove, Sub(s, e)
        trySearchingAgainBoundsContainCursor = trySearchingAgainBounds.Contains(e.Location)
        gridControl.Cursor = If(trySearchingAgainBoundsContainCursor, Cursors.Hand, Cursors.Default)
        gridView.InvalidateRect(trySearchingAgainBounds)
    End Sub

    AddHandler gridView.MouseDown, Sub(s, e)
        If trySearchingAgainBoundsContainCursor Then
            searchName = XtraInputBox.Show(String.Format("Enter {0}", "Name"), String.Format("Enter {0} dialog", "Name"), searchName)
            gridView.ActiveFilterCriteria = New DevExpress.Data.Filtering.BinaryOperator("Category_Name", searchName)
        End If
    End Sub
End Sub