find usercontrol in form

Question

1.67/5 (3 votes)

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Dear all,

I created a usercontrol called Basecontrol and then add some basecontrols into form. Then try to find all the usercontrols:

foreach (BaseControl c in this.Controls)
{
  if (c.Name == "test1")
  {
    ///////My code;         
  }

However it fails. Please help me!

Thanks in advance.

Posted 6-Jan-11 17:19pm

dnqhung

Updated 6-Jan-11 18:11pm

JF2015

v2

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4 solutions

Solution 1

Hope User Control[^] will help you.

Posted 6-Jan-11 17:22pm

Kasson

Comments

Sergey Alexandrovich Kryukov 7-Jan-11 1:11am

Sorry, Kasson. Read the question. It is about the search of control, no matter of what type. The question reads: "I created a usercontrol...".

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**JF2015** · Accepted Answer · 2011-01-06T18:15:00

Solution 3

You should do it this way:

C#

foreach (Control c in this.Controls)
{
    if(c is BaseControl)
    {
        if (c.Name == "test1")
        {
            ///////My code;
        }
    }
}

Posted 6-Jan-11 18:15pm

JF2015

Comments

Sergey Alexandrovich Kryukov 7-Jan-11 1:33am

Sure, the combined predicate may work this way. I don't see big reason to use Name property at all, because it means nothing (see also my Answer; also recursion is needed). And the type should better be generic...

jerrykid 7-Jan-11 2:01am

Good, this is another way for the answer, 5+

jerrykid · Accepted Answer · 2011-01-06T17:26:00

Solution 2

This code is not wrong if there are only BaseControl on the form. If there is other control such as TextBox, it will raise error "Cannot convert TextBox to BaseControl".

Please try:

MIDL

foreach (Control c in this.Controls)
{
if (c.Name == "test1")
{
  //Your code;
}

Posted 6-Jan-11 17:26pm

jerrykid

Updated 6-Jan-11 17:32pm

v4

Comments

Sergey Alexandrovich Kryukov 7-Jan-11 1:30am

Yes, first and foremost. My 5.

(Frankly, I did not even try to look at the code in this Question to find some sense in it :-), just written the way it should work -- see.)

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-01-06T18:46:00

Everyone forgot a control should be searched recursively:

By name:

C#

Control FindControl(Control control, string name) {
    if (control.Name == name)
        return control;
    foreach(Control child in control.Controls) {
        Control found = FindControl(control, name);
        if (found != null)
            return found;
    } //loop
    return null; //SA!!! important!
} //FindControl

The predicate is pretty bad: why by name? (Only because it was so in the Question.) Also, nobody will guarantee the name is unique in any scope.
Maybe, it's better to search by type.

The easiest way is generic. Here is how:

csl

CONTROL_TYPE FindControl<CONTROL_TYPE>(Control control)
            where CONTROL_TYPE : Control {
    if (control is CONTROL_TYPE)
        return (CONTROL_TYPE)control; //save due to the check above
    foreach (Control child in control.Controls) {
        CONTROL_TYPE found =
            FindControl<CONTROL_TYPE>(control);
        if (found != null)
            return found;
    } //loop
    return null; //SA!!! important!
} //FindControl

Generally whole design relying on search of control is pretty bad.
In some rare cases it can be useful. Anyway, it answers the question.

Good luck!