Drag and Drop Text with Cursor Movement in RadSyntaxEditor for WinForms

Environment

Product Version	Product	Author
2023.3.1114	RadTreeView for WinForms	Dinko Krastev

Description

In the following tutorial, we will demonstrate how to drag-drop text from an external source while moving the cursor to the desired drop position.

Solution

To achieve this, you can follow the steps below:

1. Set the AllowDrop property of the RadSyntaxEditor control to true.
2. Handle the DragOver event of the RadSyntaxEditor control and set the Effect property of the DragEventArgs to DragDropEffects.All. This allows the control to accept the dragged text.
3. In the DragOver event handler, move the cursor to the desired drop position by focusing the RadSyntaxEditor control and using the MoveToPosition() method.
4. Handle the DragDrop event of the RadSyntaxEditor control and insert the dropped text at the current cursor position using the Insert() method of the SyntaxEditorElement.Document property.

Here is an example implementation:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.radSyntaxEditor1.AllowDrop = true;
        this.radSyntaxEditor1.DragOver += radSyntaxEditor1_DragOver;
        this.radSyntaxEditor1.DragDrop += radSyntaxEditor1_DragDrop;
    }

    private void radSyntaxEditor1_DragDrop(object sender, DragEventArgs e)
    {
        string txt = e.Data.GetData(DataFormats.Text).ToString();
        this.radSyntaxEditor1.SyntaxEditorElement.Document.Insert(GetCaretPostion().Index, txt);
    }

    private void radSyntaxEditor1_DragOver(object sender, DragEventArgs e)
    {
        e.Effect = DragDropEffects.All;
        this.radSyntaxEditor1.SyntaxEditorElement.CaretPosition.MoveToPosition(GetCaretPostion());
        this.radSyntaxEditor1.Focus();
    }

    private CaretPosition GetCaretPostion()
    {
        Point pt = this.radSyntaxEditor1.SyntaxEditorElement.PointFromScreen(MousePosition);
        CaretPosition caretPosition = this.radSyntaxEditor1.SyntaxEditorElement.GetPositionFromControlPoint(pt);
        return caretPosition;
    }
}

Public Partial Class Form1
    Inherits Form

    Public Sub New()
        InitializeComponent()
        Me.radSyntaxEditor1.AllowDrop = True
        AddHandler Me.radSyntaxEditor1.DragOver, AddressOf radSyntaxEditor1_DragOver
        AddHandler Me.radSyntaxEditor1.DragDrop, AddressOf radSyntaxEditor1_DragDrop
    End Sub

    Private Sub radSyntaxEditor1_DragDrop(ByVal sender As Object, ByVal e As DragEventArgs)
        Dim txt As String = e.Data.GetData(DataFormats.Text).ToString()
        Me.radSyntaxEditor1.SyntaxEditorElement.Document.Insert(GetCaretPostion().Index, txt)
    End Sub

    Private Sub radSyntaxEditor1_DragOver(ByVal sender As Object, ByVal e As DragEventArgs)
        e.Effect = DragDropEffects.All
        Me.radSyntaxEditor1.SyntaxEditorElement.CaretPosition.MoveToPosition(GetCaretPostion())
        Me.radSyntaxEditor1.Focus()
    End Sub

    Private Function GetCaretPostion() As CaretPosition
        Dim pt As Point = Me.radSyntaxEditor1.SyntaxEditorElement.PointFromScreen(MousePosition)
        Dim caretPosition As CaretPosition = Me.radSyntaxEditor1.SyntaxEditorElement.GetPositionFromControlPoint(pt)
        Return caretPosition
    End Function
End Class

Make sure to add empty space in the control before dragging and dropping the text to have room for the drop operation.