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FindControl in Windows Form

Posted on 2004-09-27
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Last Modified: 2010-08-02
Hi!

I have a Windows Form and I need to find a control in the form but I can't find out how to do it in a Windows Form!
I tried this:

((TextBox)this.FindControl(Form1.ActiveForm,"cn")).Text = "my text";

            private Control FindControl(Control Parent,string Target)
            {
                  Control FoundIt = null;
                  int i=0;
                  do
                  {
                        if(Parent.Controls[i].Name == Target)
                        {
                              FoundIt = Parent.Controls[i];
                        }
                        else
                        {
                              if(Parent.Controls[i].Controls.Count > 0)
                                    FoundIt = FindControl(Parent.Controls[i], Target);
                              i++;
                        }
                  }
                  while(FoundIt!=null || i>Parent.Controls.Count);
                  return FoundIt;
            }

But it don't work, it says tat the refrence of the object is not set to a instance of an object (or something like that)
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Comment
Question by:aleborg
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10 Comments
 
LVL 48

Expert Comment

by:AlexFM
ID: 12158442
Can you describe what are you trying to do? I see that you use recursion, why? Recursive function must always have stop condition, and FindControl doesn't have it.
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LVL 19

Accepted Solution

by:
Desp earned 250 total points
ID: 12158495
Control myControl = new Control ();
foreach (Control c in this.Controls)
if (c.Name == "textBox1")
      {
      myControl = c;                              
      MessageBox.Show(myControl .Name );
      }
0
 
LVL 9

Expert Comment

by:Thalox
ID: 12158684

I think your quit-condition is not right.

try this
while(FoundIt == null && i<Parent.Controls.Count);

to stop, if found, or no more controls...

this should work,

Thalox
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LVL 9

Expert Comment

by:Thalox
ID: 12158695
...
and I would use a while-loop, not do-while, because there could be controls, with no childs
0
 

Author Comment

by:aleborg
ID: 12158797
What I'm trying to do in this code is to find a textbox with a special name.
I have some "rows" in my form, each row has a drobpdownlist and some textbox, each control in a row is named txtArt1, txtText1, txtPris1
the number, 1 is the number of the row and txtArt is the DropdownList.
All dropdownlists are connected to private void txtArt1_SelectedIndexChanged(object sender, System.EventArgs e) on selectedindexchanged.

And txtArt1_SelectedIndexChanged looks like this:
            private void txtArt1_SelectedIndexChanged(object sender, System.EventArgs e)
            {
                  ComboBox dd = ((ComboBox)sender);
                  string cn = dd.Name.Replace("txtArt","");
                  
                  FakturaDLL.Products pr = new FakturaDLL.Products();
                  if(pr.GetProduct(dd.Text))
                  {
                        ((TextBox)this.FindControl(this.ParentForm,"txtText"+cn)).Text = pr.ProdText.ToString();
                        //txtPris1.Text = pr.ProdPrice.ToString(); - do the same thing with txtPris
                  }
                  else
                        MessageBox.Show("Produkten kunde inte hittas!");
            }

So what I'm trying to do is, that when txtArt is changed, the textboxes on the same row chould be updated.
0
 

Author Comment

by:aleborg
ID: 12159392
Tried this:
      ((TextBox)this.FindControl("txtText"+cn, this.Controls)).Text = pr.ProdText.ToString();

            private Control FindControl(string Target,Control.ControlCollection cont)
            {
                  Control myControl = new Control ();
                  foreach (Control c in cont)
                  {
                        if (c.Name == Target)
                        {
                              myControl = c;                        
                        }
                        else
                        {
                              if(c.Controls.Count >0)
                                    myControl=FindControl(Target,c.Controls);
                        }
                  }
                  return myControl;
            }

But it don't work, te reason that I wan't recursion is that all controls are placed in a tabcontrol so I need to check all controls and controls in the controls in the form.
If I have all controls in the form and not in a tabcontrol and use this private Control FindControl(string Target) and don't have recursion it works!
What am I doing wrong?
0
 
LVL 19

Expert Comment

by:Desp
ID: 12166518

simply put the my code in a function which accepts a stting and returns a control.. call this function first time using:

FindControl(textBox2.Text, this);

and heres the FindControl
private void FindControl(string text, Control Parent)
{
                  
      Control myControl = new Control ();
      foreach(Control c in Parent.Controls)
      {
            if (c.Name == text)
            {
                  myControl = c;                              
                  MessageBox.Show(myControl.Name );
            }
            if (c.Controls.Count >0)
                  FindControl(text,c); // recursive call
                        
            }                  
}
0
 

Author Comment

by:aleborg
ID: 12167081
That's What I've done but it complains and says that the conversion isn't valid on this line:
((TextBox)this.FindControl("txtText"+cn, this)).Text = pr.ProdText.ToString();

My code:
            private void txtArt1_SelectedIndexChanged(object sender, System.EventArgs e)
            {
                  ComboBox dd = ((ComboBox)sender);
                  string cn = dd.Name.Replace("txtArt","");
                  
                  FakturaDLL.Products pr = new FakturaDLL.Products();
                  if(pr.GetProduct(dd.Text))
                  {
                        ((TextBox)FindControl("txtText"+cn, this)).Text = pr.ProdText.ToString();
                        ((TextBox)FindControl("txtPris"+cn, this)).Text = pr.ProdPrice.ToString();
                  }
                  else
                        MessageBox.Show("Produkten kunde inte hittas!");
            }
            
            private Control FindControl(string Target,Control Parent)
            {

                  Control myControl = new Control ();
                  foreach (Control c in Parent.Controls)
                  {
                        if (c.Name == Target)
                        {
                              myControl = c;
                        }
                        else
                        {
                              if(c.Controls.Count >0)
                                    myControl = FindControl(Target,c);
                        }
                  }
                  return myControl;    
            }
if i do this in FindControl:
if (c.Name == Target)
{
      myControl = c;
      MessageBox.Show(c.Name);
}
Then I can see that the right name is returned so nothing seems to be wrong with the function
0
 

Author Comment

by:aleborg
ID: 12167346
Solved it:
         private Control FindControl(string Target,Control Parent)
          {

               Control myControl = new Control ();
               foreach (Control c in Parent.Controls)
               {
                    if (c.Name == Target)
                    {
                         myControl = c;
                         break;
                    }
                    else
                    {
                         if(c.Controls.Count >0)
                              myControl = FindControl(Target,c);
                    }
               }
               return myControl;    
          }
0
 
LVL 12

Expert Comment

by:starlite551
ID: 33338701
private Control FindControl(string controlName,Control Parent)
{
               Control ct = new Control();
               bool flag = false;
               
               foreach(Control c in Parent.Controls)
               {
                         if(c.Name == controlName)
                         {
                                    ct = c;  
                                    falg = true;
                         }    
               }

               if(flag == true)
               {
                       retrun ct;
               }
               return null;  
}
0

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