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WPF-VB6 Interop causes a timer runtime error

I created the following test script to track error using VB6-WPF interaction:

There is a .Net WPF DLL that displays a form with a text field. The text field does not process keyboard input - there is no data binding, there is no event handler. DLL - COM visible.

A VB6.exe calls the ShowWindow DLL function to display a WPF form. When I enter any key into the text box, it causes a "Runtime Error" 6 "Overflow" error in the VB application. The error occurs in the line "dVal = 0" of the Timer1 event.

I assume that the error is due to the fact that an unhandled key event bubbles up before the VB6 application. Should WPF events go up to VB6? Why does the problem occur in the timer? Why does this only happen if a double variable is set? This does not happen if the string "dVal = 0" is missing. Any thoughts?

C # code from an open class that displays a window:

public class NetFormIFace : INetFormIFace
{

    public void ShowWindow1()
    {
        Window1 w1;
        w1 = new Window1();
        w1.Show();
    }

}

XAML for the window. Nothing is added to the code:

<Window x:Class="SSEC.NetForm.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window1" Height="300" Width="300">
    <Canvas>
        <TextBox Height="34" Canvas.Left="35" TextWrapping="Wrap" Text="TextBox" Canvas.Top="52" Width="94" />
    </Canvas>
</Window>

VB6 Code:

Option Explicit

Dim IFace As NetFormIFace

Private Sub Command1_Click()
    IFace.ShowWindow1
End Sub

Private Sub Form_Load()
    Set IFace = New NetFormIFace
    Timer1.Interval = 50
    Timer1.Enabled = True
End Sub

Private Sub Timer1_Timer()
    Dim iVal As Integer
    Dim dVal As Double

    iVal = 0    ' Does not cause an error
    dVal = 0    ' Causes an error
End Sub
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2 answers

WPF, VB6. : Win32 WPF. , , VB6.

Win32 VB6 HwndSource WPF , : WPF Win32.

WPF Composite Control ActiveX VB6. -, , VB.NET WinForms UserControl, . WPF Composite Control Windows Forms. WinForms UserControl ActiveX VB6 Microsoft InteropForms Toolkit. , , .

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, , VB6, GUI. . , .

Private Sub Timer1_Timer()
    Dim iVal As Integer
    Dim dVal As Double
    Dim lTemp as long

    lTemp = Timer1.Interval ' The error does not occur if this (any GUI?) element is read. I don't know why.

    iVal = 0    ' Does not cause an error
    dVal = 0    ' Causes an error
End Sub
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