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    Selection Service

    The ISelectionService interface exposes selection-related operations for a WinFormHtmlEditor control. It is reached through the Selection property on the editor: htmlEditor1.Selection.SelectAll(). Methods cover programmatic text selection (by index range, by search text, or by HTML element), inspection of what is currently selected, and helpers for whitespace trimming and length queries.

    The interface implements IDisposable because the runtime implementation holds a reference to the underlying MSHTML selection object. The editor disposes the service when the control itself is disposed, so application code never needs to call Dispose directly.

    Namespace: SpiceLogic.HtmlEditor.Abstractions.Services
    Assembly: SpiceLogic.HtmlEditor.Abstractions
    Inheritance: ISelectionService : IDisposable

    SelectText(Int32, Int32) Method

    Selects a range of characters in the document body, starting at startIndex and continuing for length characters. Use this overload when you already know the exact extents of the range to highlight.

    Syntax
    void SelectText(int startIndex, int length);
    Parameters
    NameTypeDescription
    startIndexInt32Zero-based character offset within the body where the selection begins.
    lengthInt32Number of characters to include in the selection.
    Returns

    None.

    Remarks

    Indexes count characters in the rendered text stream, not bytes in the raw HTML source. Call htmlEditor1.Selection.GetSelectionLength() afterwards to confirm the highlighted range.

    Example
    // Highlight the first 12 characters of the document.

htmlEditor1.Focus();

htmlEditor1.Selection.SelectText(0, 12);

Debug.WriteLine($"Selected: {htmlEditor1.Selection.GetSelectedText()}");

    SelectText(Int32) Method

    Selects from startIndex to the end of the body. Useful for "select to end" affordances such as Shift+End in a paragraph.

    Syntax
    void SelectText(int startIndex);
    Parameters
    NameTypeDescription
    startIndexInt32Zero-based character offset within the body where the selection begins.
    Returns

    None.

    Example
    // Select everything from the 20th character to the end of the body.
htmlEditor1.Selection.SelectText(20);
int len = htmlEditor1.Selection.GetSelectionLength();
Debug.WriteLine($"Selected {len} characters to end of body.");
    ' Select everything from the 20th character to the end of the body.
htmlEditor1.Selection.SelectText(20)
Dim len As Integer = htmlEditor1.Selection.GetSelectionLength()
Debug.WriteLine($"Selected {len} characters to end of body.")

    SelectText(String, Boolean, Boolean, Boolean) Method

    Searches the document body for text and, if found, selects the first match. Supports forward and backward search, whole-word matching, and case-sensitive matching - the same options offered by a typical Find dialog.

    Syntax
    bool SelectText(string text, bool forward, bool matchWholeWord, bool matchCase);
    Parameters
    NameTypeDescription
    textStringThe text to search for.
    forwardBooleantrue to search forward from the current caret position; false to search backward.
    matchWholeWordBooleantrue to require word-boundary matches; false to allow matches inside larger words.
    matchCaseBooleantrue for case-sensitive matching; false for case-insensitive.
    Returns

    true if a match was found and selected; otherwise false.

    Example
    bool found = htmlEditor1.Selection.SelectText("Contoso", forward: true, matchWholeWord: true, matchCase: false);
if (!found)
{
    MessageBox.Show("Not found");
}
    Dim found As Boolean = htmlEditor1.Selection.SelectText("Contoso", forward:=True, matchWholeWord:=True, matchCase:=False)

If Not found Then
    MessageBox.Show("Not found")
End If

    SelectHtmlElement(IHTMLElement) Method

    Selects the entire HTML element passed in, including all of its descendants. The selection visibly highlights the element's rendered area.

    Syntax
    void SelectHtmlElement(IHTMLElement element);
    Parameters
    NameTypeDescription
    elementmshtml.IHTMLElementThe MSHTML element to select. Typically obtained from htmlEditor1.StateQuery.GetActiveHtmlElement() or from a DOM walk.
    Returns

    None.

    Example
    // Highlight the element under the caret.
IHTMLElement active = htmlEditor1.StateQuery.GetActiveHtmlElement();
if (active != null)
{
    htmlEditor1.Selection.SelectHtmlElement(active);
}
    ' Highlight the element under the caret.
Dim active As IHTMLElement = htmlEditor1.StateQuery.GetActiveHtmlElement()

If active IsNot Nothing Then
    htmlEditor1.Selection.SelectHtmlElement(active)
End If

    GetSelectionInfo Method

    Returns a snapshot of the current selection, including its zero-based start index, length, plain text, and inner HTML.

    Syntax
    SelectionInfo GetSelectionInfo();
    Returns

    A SelectionInfo instance with these public fields:

    FieldTypeDescription
    StartIndexInt32Zero-based offset of the selection start within the body.
    LengthInt32Length of the selection in characters.
    TextStringThe selected text (no markup).
    HtmlStringThe selected HTML fragment.
    Example
    SelectionInfo info = htmlEditor1.Selection.GetSelectionInfo();

Debug.WriteLine($"{info.StartIndex}+{info.Length}: {info.Text}");

Debug.WriteLine($"HTML: {info.Html}");

    DeselectAll Method

    Clears the current selection so that no HTML elements are selected in the editor. Equivalent in spirit to TextBox.DeselectAll() on a .NET TextBox: the caret remains visible, but nothing is highlighted.

    Syntax
    void DeselectAll();
    Returns

    None.

    Example
    // Drop any active selection after applying a programmatic change.

htmlEditor1.Selection.SelectAll();

htmlEditor1.Formatting.SetFontSize(12);

htmlEditor1.Selection.DeselectAll();

    Unselect Method

    Removes the current selection. Functionally a synonym for DeselectAll; retained for parity with the underlying MSHTML unselect command.

    Syntax
    void Unselect();
    Returns

    None.

    Example
    // Same effect as DeselectAll. Kept for source compatibility.

htmlEditor1.Selection.Unselect();

    SelectAll Method

    Selects the entire document body. Equivalent to pressing Ctrl+A while the editor has focus.

    Syntax
    void SelectAll();
    Returns

    None.

    Example
    // Select everything, then read the plain text.
htmlEditor1.Selection.SelectAll();
string body = htmlEditor1.Selection.GetSelectedText();
Debug.WriteLine($"Body length: {body.Length}");
    ' Select everything, then read the plain text.
htmlEditor1.Selection.SelectAll()
Dim body As String = htmlEditor1.Selection.GetSelectedText()
Debug.WriteLine($"Body length: {body.Length}")

    GetSelectedHtml Method

    Returns the HTML fragment that represents the current selection, including all inline tags inside the range.

    Syntax
    string GetSelectedHtml();
    Returns

    The selected HTML as a string. An empty string is returned when nothing is selected.

    Example
    string html = htmlEditor1.Selection.GetSelectedHtml();
if (!string.IsNullOrEmpty(html))
{
    Clipboard.SetText(html);
}
    Dim html As String = htmlEditor1.Selection.GetSelectedHtml()

If Not String.IsNullOrEmpty(html) Then
    Clipboard.SetText(html)
End If

    GetSelectedText Method

    Returns the plain text of the current selection, with all HTML markup stripped.

    Syntax
    string GetSelectedText();
    Returns

    The selected text as a string. An empty string is returned when nothing is selected.

    Example
    string text = htmlEditor1.Selection.GetSelectedText();
label1.Text = $"Selected: {text}";
    Dim text As String = htmlEditor1.Selection.GetSelectedText()
label1.Text = $"Selected: {text}"

    TrimSelection(TrimDirections) Method

    Trims whitespace from the start, the end, or both ends of the current selection, then returns the trimmed text. Useful when a user double-clicks a word that picked up trailing whitespace and you want a clean token.

    Syntax
    string TrimSelection(TrimDirections trimDirection = TrimDirections.Both);
    Parameters
    NameTypeDescription
    trimDirectionTrimDirectionsStart trims leading whitespace, End trims trailing whitespace, Both (default) trims both ends.
    Returns

    The trimmed selection text as a string.

    Example
    htmlEditor1.Selection.SelectText("  hello world  ", true, false, true);
string clean = htmlEditor1.Selection.TrimSelection(TrimDirections.Both);
Debug.WriteLine($"Clean token: '{clean}'");
    htmlEditor1.Selection.SelectText("  hello world  ", True, False, True)
Dim clean As String = htmlEditor1.Selection.TrimSelection(TrimDirections.Both)
Debug.WriteLine($"Clean token: '{clean}'")

    GetSelectionLength Method

    Returns the length, in characters, of the current selection. Returns 0 when nothing is selected.

    Syntax
    int GetSelectionLength();
    Returns

    Integer character count of the current selection.

    Example
    if (htmlEditor1.Selection.GetSelectionLength() == 0)
{
    MessageBox.Show("Please select some text first.");
    return;
}
    If htmlEditor1.Selection.GetSelectionLength() Is 0 Then
    MessageBox.Show("Please select some text first.")
    Return
End If

    Dispose Method

    Inherited from IDisposable. Called by the editor control during teardown so it can release the underlying MSHTML selection object. Host applications normally do not invoke this directly.

    Syntax
    void Dispose();
    Returns

    None.

    Example
    // Disposing the editor disposes its services automatically.

htmlEditor1.Dispose();

// Equivalent of explicitly disposing the selection service - not normally needed:

// htmlEditor1.Selection.Dispose();

    Last updated on May 14, 2026