Displaying Child forms as Modal Dialog

I've tried various approaches on my Windows 7 machine such as calling the API function SetParent and handling the dialog's LocationChanged event to ensure it stayed within the parent's bounds - but none of them would work :(

What does work is to set the dialog's start position to 'CenterParent' and then handle its WndProc to intercept the SC_MOVE message and prevent it from being moved at all.

If that's of interest, the code is as follows:

// on parent from

ChildForm frmChild = new ChildForm();

frmChild.StartPosition = FormStartPosition.CenterParent;

frmChild.ShowDialog(this);

// on child form

const int WM_SYSCOMMAND = 0x0112;

const int SC_MOVE = 0xF010;

protected override void WndProc(ref Message m)

{

switch(m.Msg)

{

case WM_SYSCOMMAND :

int command = m.WParam.ToInt32() & 0xfff0;

if (command == SC_MOVE) return;

break;

}

base.WndProc(ref m);

}

2 Replies

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Vulpes15y ago
Accepted answer
I've tried various approaches on my Windows 7 machine such as calling the API function SetParent and handling the dialog's LocationChanged event to ensure it stayed within the parent's bounds - but none of them would work :(

What does work is to set the dialog's start position to 'CenterParent' and then handle its WndProc to intercept the SC_MOVE message and prevent it from being moved at all.

If that's of interest, the code is as follows:

// on parent from

ChildForm frmChild = new ChildForm();
frmChild.StartPosition = FormStartPosition.CenterParent;
frmChild.ShowDialog(this);

// on child form

const int WM_SYSCOMMAND = 0x0112;
const int SC_MOVE = 0xF010;

protected override void WndProc(ref Message m)
{
switch(m.Msg)
{
case WM_SYSCOMMAND :
int command = m.WParam.ToInt32() & 0xfff0;
if (command == SC_MOVE) return;
break;
}

base.WndProc(ref m);
}
sasikumar15y ago
This was a great(differnt) approach to the problem. It worked. Thanks much.