Completed
Last Updated: 11 Nov 2025 08:11 by ADMIN
Release Telerik UI for WPF 2025.4.1111 (2025 Q4)
Martin Ivanov
Created on: 10 Oct 2025 15:44
Category: SyntaxEditor
Type: Bug Report
SyntaxEditor: NullReferenceException thrown on opening the CompletionListWindow when RadSyntaxEditor is hosted in a non-WPF application and there is no WPF Application and MainWindow initialized
NullReferenceException thrown on opening the CompletionListWindow when RadSyntaxEditor is hosted in a non-WPF application (usually WinForms) and there are no WPF Application and MainWindow initialized.
This can happen if the RadSyntaxEditor for WPF is hosted in a WinForms application. In this scenario the System.Windows.Application.Current and its MainWindow are not initialized, which is what the IntelliPrompt positioning logic relies on.
Exception details:
System.NullReferenceException: 'Object reference not set to an instance of an object.' > Telerik.Windows.Controls.SyntaxEditor.dll!Telerik.Windows.Controls.SyntaxEditor.UI.IntelliPromptBase.SetPosition(System.Windows.Point pointInScreen) Line 452 C# Telerik.Windows.Controls.SyntaxEditor.dll!Telerik.Windows.Controls.SyntaxEditor.UI.IntelliPromptBase.SetPosition(System.Windows.Point pointInEditorPresenter, System.Windows.Point pointAboveTheCaret) Line 442 C# Telerik.Windows.Controls.SyntaxEditor.dll!Telerik.Windows.Controls.SyntaxEditor.UI.IntelliPromptBase.SetPositionInView() Line 480 C# Telerik.Windows.Controls.SyntaxEditor.dll!Telerik.Windows.Controls.SyntaxEditor.UI.IntelliPromptBase.InitializeIntellisense() Line 401 C# Telerik.Windows.Controls.SyntaxEditor.dll!Telerik.Windows.Controls.SyntaxEditor.UI.IntelliPromptBase.Show(Telerik.Windows.Controls.SyntaxEditor.UI.CaretPosition caretStartPosition, Telerik.Windows.Controls.SyntaxEditor.UI.CaretPosition caretEndPositions) Line 211 C# Telerik.Windows.Controls.SyntaxEditor.dll!Telerik.Windows.Controls.SyntaxEditor.UI.IntelliPromptBase.Show() Line 182 C#To work this around, you can initialize a new WPF application and MainWindow and create a hidden HwndSource for the MainWindow. This should happen before showing the WPF content in the WinForms application's code.
public Form1() { InitializeComponent(); new System.Windows.Application(); System.Windows.Application.Current.MainWindow = new System.Windows.Window(); var parameters = new HwndSourceParameters("HiddenHost") { Width = 1, Height = 1, WindowStyle = unchecked((int)0x80000000) // WS_POPUP | WS_EX_NOACTIVATE }; var hwndSource = new HwndSource(parameters); hwndSource.RootVisual = System.Windows.Application.Current.MainWindow; // other code here ElementHost host = new ElementHost { Dock = DockStyle.Fill }; host.Child = wpfControl this.Controls.Add(host); }
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