Dynamically Adding Controls to a Windows Form - Handling the Mouse Up Event
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The Mouse Up event handler does not contain many surprises. Here is how it looks:
private void cbName_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e) {
// Cast the sender object to the check box
// that received the mouse up event.
CheckBox cbName = (CheckBox) sender;
// Locate the associated numeric up down from our hash table of controls.
// The key is the text of the check box (stored previously)
NumericUpDown nudName = (NumericUpDown) nudControls[cbName.Text];
// Get out the current value
int val = (int) nudName.Value;
// Figure out which button they clicked.
if (e.Button == MouseButtons.Left) {
val++;
} else if (e.Button == MouseButtons.Right) {
val--;
if (val < 0) {
val = 0;
}
}
// Set the value of the numeric up down
nudName.Value = val;
// Check to see if we should have the checkbox checked
if (val == 0) {
cbName.Checked = false;
} else {
cbName.Checked = true;
}
}
Again, the idea here is that we want to increase the value of the associated numeric up down if the left mouse was clicked, and decrease the value if the right button was clicked.
First, we know what specific checkbox we are dealing with because the method passes in the sender object, in this case the desired check box. We immediately cast it to a CheckBox object so we can access and modify some of its parameters.
Next, the trick is getting the appropriate numeric up down control. Recall that when we created the control, we added it to an internal hash table called nudControls, using the name of the medication as a key. This also happens to be the Text property of the checkbox. So we can easily locate the numeric up down control that we need by asking for it by the value of the checkbox Text parameter.
We then perform the appropriate logic, and our method is complete!
Resizing the Form
Last, I thought it would be nice to include a method that would change the size (height) of the form. Since I would not know how many controls I would be adding at design time, I knew that if I wanted all of the controls to be visible to the end-user I would have to handle this dynamically. Here is the method:
private void SizeToFit() {
// If called after the dynamic controls were created,
// vertPos is now the last vertical position of the
// last item added. Resize the form, adding some bottom spacing.
Size size = new Size(this.Size.Width, vertPos + 27);
this.ClientSize = size;
}
No surprises, right? I call this method from the constructor, immediately after loading the dynamic controls and calling InitializeComponent.
Summary
And there you have it! Not only did I find that this saved me a great deal of work, but deployment became simple. Likewise, future maintenance and modification was a snap. All I had to do was change an XML file, and the next time the form was loaded, all of the items would be placed in their appropriate location, with the appropriately sized dialog. Simple and effective, my favorite kind of software.
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