How set the background of an MDI container window?

Philippe Mori

I would think you need to do P/Invoke for that...

Philippe Mori

Dave Kreskowiak

You could, but it's worthess and will slow down your applications rendering speed. Again, you can't do it as design time. You have to do it at runtime. Again, you have to enumerate through the MdiParent Controls collection. Once you find the MdiClient control, you can set its BackgroundImage property to whatever you want.

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Dave Kreskowiak

BillWoodruff

If your question means you want a solution where there is one MDI container Form with a background image, and all the Forms on it ... interpreting "client" to meaning an 'mdi child form:' someForm.MdiParent = MDIContainerForm ... show a background as if they were 'transparent,' and you were seeing the portion of the MDIContainerForm's background their current bounding-box covers ... You are in for some deep-plumbing, and as others comment here, it ain't worth it. Now if the MDI container form just has a background that's a texture, then it's easy, but I'm pretty sure you are asking about the container form having a background picture, not a texture. However, if you have the option of not using the MDI architecture, there are some ways you can 'simulate' the effect of contained Forms having the same background image. You make them transparent, and you "do the right thing" so that at run-time they remain in the boundary of the intended container control. If you wish to hear about the specifics of this alternative, just ask. best, Bill

"Last year I went fishing with Salvador Dali. He was using a dotted line. He caught every other fish." Steven Wright

Alisaunder

You can set the background by casting the type to MDIClient and setting the MDIClient background. EXAMPLE:

    private void Form1\_Load(object sender, EventArgs e)
    {
        MdiClient ctlMDI;
        //' Loop through all of the form's controls looking
        //' for the control of type MdiClient.
        foreach (Control ctl in this.Controls)
        {                
            try
            {
                // Attempt to cast the control to type MdiClient.
                ctlMDI = (MdiClient)ctl;
                
                // Set the BackColor of the MdiClient control.
                ctlMDI.BackColor = Color.White;
            }
            catch (InvalidCastException exc)
            {
                // Catch and ignore the error if casting failed.
            }
        }
    }

Luc Pattyn

Alisaunder wrote:

try { // Attempt to cast the control to type MdiClient. ctlMDI = (MdiClient)ctl;

That is so ugly. I suggest you read up on the is and as keywords. :doh:

Luc Pattyn [My Articles] Nil Volentibus Arduum

Dave Kreskowiak

Not to mention using a try/catch to find the correct control is slow as exceptions are expensive objects to create. Exceptions should be used to handle exceptional cases, not used in main logic. A much better and faster implementation would have been to check the type of the control first, then cast it to an MdiClient if appropriate.

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Dave Kreskowiak

Alisaunder

That's funny considering this comes from Microsoft's own help and support on the subject. http://support.microsoft.com/kb/319417[^]

Dave Kreskowiak

I don't care. Those examples are not there to demo best practices. Those examples are not considered "production-level" code.

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Dave Kreskowiak

Alisaunder

I'm so glad your opinion isn't all that matters then.

Dave Kreskowiak

I'm not the only one telling you the practice sucks...

A guide to posting questions on CodeProject[^]
Dave Kreskowiak

Alisaunder

And yet neither of you are displaying an alternative that is better?

BillWoodruff

Hi, I don't think you deserve to be cast into the outer darkness of the dreaded one-vote here, because you were, I think, sincerely trying to respond to the OP's question. And, whether the code you provided leads to gnashing of teeth, or not, it does work. But, may I suggest, in the future, you provide a link to the MS docs, or other sources, code examples are taken from. best, Bill

"Last year I went fishing with Salvador Dali. He was using a dotted line. He caught every other fish." Steven Wright

BillWoodruff

+5 Right on target, Dave, and you reminded me of when ... several years ago ... I did some stuff with MDI (yuck), and I went back today, and took a look at the MdiClient component that is created when you set a Form's IsMdiContainer Property = true. The WinForms designers, probably having a bad hair day, set the Text and Name properties of MdiClient to an empty string, which means you can't do something like this to find it:

//
private MdiClient theMDIClientControl;
//
// note: don't need to recurse
Control[] potentialMDIClientControls = this.Controls.Find("MdiClient", false);
//
if (potentialMDIClientControls.Length > 0) theMDIClientControl = potentialMDIClientControls[0] as MdiClient;

So, as you said, you gotta iterate/enumerate over the Controls collection of the Form.

"Last year I went fishing with Salvador Dali. He was using a dotted line. He caught every other fish." Steven Wright

Luc Pattyn

I'm not in the spoon feeding business, I did provide the two keywords that exist for dealing elegantly with such situations. So if you want to learn something, look them up and read the reference material. :|

Luc Pattyn [My Articles] Nil Volentibus Arduum

Dave Kreskowiak

Apparently you haven't been reading the posts. You also apparently won't be happy until you see actual code:

private void MdiClientExample()
{
foreach (Control c in this.Controls)
{
if (c is MdiClient)
{
MdiClient mc = (MdiClient)c;
...
}
}
}

Are you happy now? Oh, and by the way, I don't consider this production quality code either. It's just cleaner than the example Microsoft gave. And if you're going to critisize us, you might want to start by creating your own code samples instead of lifting and posting others as your own work.

A guide to posting questions on CodeProject[^]
Dave Kreskowiak

Alisaunder

So sorry you don't feel like trying to answer the ops question with something less cryptic. Seems forums just aren't as helpful as they used to be. Since you feel you are such an expert that you you don't need to provide examples my opinion, for what it's worth is that you are no help at all and shouldn't even be posting.

Dave Kreskowiak

Yeah, right. A couple of Code Project MVP's aren't very helpful at all. The pile of 5-voted responses to questions just doesn't offer up any evidence at all of us being helpful. I'm not in the spoon-feed business either. There are just WAY too many very basic concept questions being asked that are very easily answered simply by typing the question into Google. I'd rather have someone learn how to do research themselves than just keep asking question after question about very basic topics.

A guide to posting questions on CodeProject[^]
Dave Kreskowiak

Alisaunder

Actually Most everyone I know searches for the answers before hitting a forum with a question. Personally in my opinion it's more professional to offer assistance with a basic code example in the hopes the op learns something in the process. All anyone is learning from your responses is not to ask you for help.

Dave Kreskowiak

Very true. I found the lack of a name a little annoying at first, but I now prefer to find it by type. You really can't change the type at all, but the name can be changed breaking existing code.

A guide to posting questions on CodeProject[^]
Dave Kreskowiak

BillWoodruff

Alisaunder wrote:

And yet neither of you are displaying an alternative that is better?

I think the absence of code here is not the result of any 'negative intention:' It's just obvious that the best practice here is to enumerate the controls on the Form [1], test each one using the 'Is operator, and, when the MdiClient Control is found, then cast it from Type Control back to its 'native Type, 'MdiClient ... at which point you can have your way with it.

//
// assume you have loaded a valid image from an embedded resource
// into the variable of Type Bitmap named 'mdiBackGround'
//
private MdiClient theMDIClientControl;
//
foreach (Control theControl in this.Controls) [2]
{
if (theControl is MdiClient)
{
theMDIClientControl = theControl as MdiClient;
break;
}
}

if (theMDIClientControl != null) theMDIClientControl.BackgroundImage = mdiBackGround;

[1] see my response to Dave K. above[^] confirming why it is absolutely necessary to enumerate the Controls on the Form. [2] Seems a reasonable assumption the MdiClient Control will always be in the top-level Form Control Collection: hence no need for a recursive search

"Last year I went fishing with Salvador Dali. He was using a dotted line. He caught every other fish." Steven Wright