New to Telerik UI for WinForms? Download free 30-day trial

Custom Taggers

To create a custom tagger, you can inherit from the abstract generic TaggerBase class. You then need to implement the abstract GetTags method which is responsible for acquiring all spans of tags which meet a specific condition.

To demonstrate this we will create the following class which shows a tool-tip on all occurrences of a specified search word.

Registering taggers

public class SimpleToolTipTagger : TaggerBase<ToolTipTag>
    private string searchWord;
    public SimpleToolTipTagger(ITextDocumentEditor editor)
        : base(editor)
    public override IEnumerable<TagSpan<ToolTipTag>> GetTags(NormalizedSnapshotSpanCollection spans)
        if (string.IsNullOrEmpty(this.searchWord))
            yield break;
        TextSnapshot snapshot = this.Document.CurrentSnapshot;
        foreach (TextSnapshotSpan snapshotSpan in spans)
            string lineString = snapshotSpan.GetText();
            int index = lineString.IndexOf(this.searchWord);
            while (index != -1)
                TextSnapshotSpan tempSnapshotSpan = new TextSnapshotSpan(snapshot,
                    new Span(snapshotSpan.Start + index, searchWord.Length));
                yield return new TagSpan<ToolTipTag>(tempSnapshotSpan, new ToolTipTag("Sample tooltip " + searchWord));
                index = lineString.IndexOf(this.searchWord, index + this.searchWord.Length);
    public void UpdateSearchWord(string newSearchWord)
        this.searchWord = newSearchWord;

Public Class SimpleToolTipTagger
    Inherits TaggerBase(Of ToolTipTag)
    Private searchWord As String
    Public Sub New(ByVal editor As ITextDocumentEditor)
    End Sub
    Public Overrides Iterator Function GetTags(ByVal spans As NormalizedSnapshotSpanCollection) As IEnumerable(Of TagSpan(Of ToolTipTag))
        If String.IsNullOrEmpty(Me.searchWord) Then
        End If
        Dim snapshot As TextSnapshot = Me.Document.CurrentSnapshot
        For Each snapshotSpan As TextSnapshotSpan In spans
            Dim lineString As String = snapshotSpan.GetText()
            Dim index As Integer = lineString.IndexOf(Me.searchWord)
            While index <> -1
                Dim tempSnapshotSpan As TextSnapshotSpan = New TextSnapshotSpan(snapshot, New Span(snapshotSpan.Start + index, searchWord.Length))
                Yield New TagSpan(Of ToolTipTag)(tempSnapshotSpan, New ToolTipTag("Sample tooltip " & searchWord))
                index = lineString.IndexOf(Me.searchWord, index + Me.searchWord.Length)
            End While
    End Function
    Public Sub UpdateSearchWord(ByVal newSearchWord As String)
        Me.searchWord = newSearchWord
    End Sub
End Class

To use the tagger you need to register it in the TaggersRegistry as you would do with any other tagger. You can then call the UpdateSearchWord method to apply the tagger to any spans containing a specific word.

Using the custom tagger

SimpleToolTipTagger simpleToolTipTagger = new SimpleToolTipTagger(this.radSyntaxEditor1.SyntaxEditorElement);
if (!this.radSyntaxEditor1.TaggersRegistry.IsTaggerRegistered(simpleToolTipTagger))

Dim simpleToolTipTagger As SimpleToolTipTagger = New SimpleToolTipTagger(Me.RadSyntaxEditor1.SyntaxEditorElement) 
If Not Me.RadSyntaxEditor1.TaggersRegistry.IsTaggerRegistered(simpleToolTipTagger) Then
End If 

The custom tool-tip tagger

WinForms RadSyntaxEditor with custom tool-tip tagger

See Also

In this article