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[.net] C#: Set text box from a static method


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#1 hungryhippo5000   Members   -  Reputation: 198

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Posted 06 June 2007 - 08:31 AM

Hi, I have a method such as this: private static void foo() {...} Now I would like to set the text in a text box on my form to some value from within this function, how can I achieve this?

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#2 Codejack   Members   -  Reputation: 100

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Posted 06 June 2007 - 09:02 AM

Hmmm in ASP.Net you could do something like:


public static void SetTextBoxValue(System.Web.UI.Page FormPage, String ControlName, String Value)
{
object FormControl = FormPage.FindControl(ControlName);

if (FormControl == null)
return;

((System.Web.UI.WebControls.TextBox)FormControl).Text = Value;
}



If you are not talking about ASP.Net I still reckon you would be able to search for the control from a root element somehow.

#3 hungryhippo5000   Members   -  Reputation: 198

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Posted 06 June 2007 - 09:08 AM

Thank you for the response but I'm looking for a solution for a desktop application.

#4 Codejack   Members   -  Reputation: 100

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Posted 06 June 2007 - 09:49 AM

OK then if I were to adapt the code for a Windows Forms application it would look like:


private static void ChangeText(System.Windows.Forms.Form CurrentForm, String ControlName, String Value)
{
Control TempControl = CurrentForm.Controls[ControlName];

if (TempControl != null)
{
((TextBox)TempControl).Text = Value;
}
}




As an example, I would call it from in the application like:

ChangeText(this, "TextBox1", "New textbox text");

(assume the textbox control you want to change has the name "TextBox1").

#5 kanato   Members   -  Reputation: 568

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Posted 06 June 2007 - 11:53 AM

To make that work, you need to pass the form as an argument to the method ("..." representing other arguments):

class MyForm {
public static void DoSomething(MyForm frm, ...) {
frm.textBox1.Text = "Something";
}
}

// elsewhere:
MyForm.DoSomething(theForm, ...)


If you need to access controls on the Form from within a static method, then you should ask yourself why you really want that method to be static. A non-static method would be called like:

theForm.DoSomething(...)

which (usually) makes more sense.

#6 hungryhippo5000   Members   -  Reputation: 198

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Posted 06 June 2007 - 04:49 PM

Thank you all for your response, unfortunately I still haven’t been able to solve my problem and I think it is partly my fault for not specifically stating my problem. My code is as follows:


public void ValidXmlDoc()
{
// some code before this
settings.ValidationEventHandler += new ValidationEventHandler (ValidationCallBack);
// some code after this
}

private static void ValidationCallBack(object sender, ValidationEventArgs e)
{
MessageBox.Show(e.Message, "Error");
}



What I want to do is capture that the error in ValidationCallBack and dump it in a text box, my problem is I can't do this because ValidationCallBack is a static function and I can’t pass any parameters to it. If someone could suggest a solution it would be greatly appreciated.


#7 Nypyren   Crossbones+   -  Reputation: 4302

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Posted 06 June 2007 - 04:54 PM

In C#, event handlers don't have to be static. :D!

#8 hungryhippo5000   Members   -  Reputation: 198

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Posted 06 June 2007 - 05:00 PM

WOW! Such a simple solution! Thank you! But just for sake of knowing, how would you solve this problem if it had to be static?

#9 Nypyren   Crossbones+   -  Reputation: 4302

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Posted 06 June 2007 - 05:08 PM

You'd have to make either the textbox, the form, or something in-between static. Usually you want to avoid static as much as possible though (I only really use 'static' on functions that don't really need an instance of a class. But in your case you need an instance in order to get at the text box member (well, I assume your validation functions are inside your Form or one of your UserControl classes).



static TextBox tbErrorMessage; // to serve as a reference to the main instance of the text box. You wouldn't actually want to "new TextBox" and assign to this.

public void ValidXmlDoc()
{
// some code before this

tbErrorMessage = blah; //(however you would access your text box using a non-static function)

settings.ValidationEventHandler += new ValidationEventHandler(ValidationCallBack);
// some code after this
}

private static void ValidationCallBack(object sender, ValidationEventArgs e)
{
tbErrorMessage.Text = "VALIDATION FAILED! D:";
}







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