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c#winformsvalidationbutton
Liger86
Liger86

Reputation: 35

How can I utilize Validating/Validated event in Button class?

I understand how validated event works with textbox but I don't understand how it's triggered with button on a form.

MSDN doesn't have validated/validating listed in their documentation.

However, both properties are listed as events in properties window. enter image description here

Upvotes: 1

Views: 9529

Answers (3)

Niranjan Singh
Niranjan Singh

Reputation: 18290

You are visiting wrong documentation page of MSDN. You should go through Button Events, there you can find help about Validated and Validating events.

Each Control-derived object has two events named Validating and Validated. Also it has a property called CausesValidation. When this is set to true (it is true by default) then the control participates in validation. Otherwise, it does not.

Example:

private void textBox1_Validating(object sender, 
                System.ComponentModel.CancelEventArgs e)
{
   string errorMsg;
   if(!ValidEmailAddress(textBox1.Text, out errorMsg))
   {
      // Cancel the event and select the text to be corrected by the user.
      e.Cancel = true;
      textBox1.Select(0, textBox1.Text.Length);

      // Set the ErrorProvider error with the text to display.  
      this.errorProvider1.SetError(textBox1, errorMsg);
   }
}

private void textBox1_Validated(object sender, System.EventArgs e)
{
   // If all conditions have been met, clear the ErrorProvider of errors.
   errorProvider1.SetError(textBox1, "");
}
public bool ValidEmailAddress(string emailAddress, out string errorMessage)
{
   // Confirm that the e-mail address string is not empty. 
   if(emailAddress.Length == 0)
   {
      errorMessage = "e-mail address is required.";
         return false;
   }

   // Confirm that there is an "@" and a "." in the e-mail address, and in the correct order.
   if(emailAddress.IndexOf("@") > -1)
   {
      if(emailAddress.IndexOf(".", emailAddress.IndexOf("@") ) > emailAddress.IndexOf("@") )
      {
         errorMessage = "";
         return true;
      }
   }

   errorMessage = "e-mail address must be valid e-mail address format.\n" +
      "For example '[email protected]' ";
      return false;
}

Edit:
Source:

The biggest problem with validation on WinForms is the validation is only executed when the control has "lost focus". So the user has to actually click inside a text box then click somewhere else for the validation routine to execute. This is fine if your only concerned about the data that is entered being correct. But this doesn't work well if you're trying to make sure a user didn't leave a textbox empty by skipping over it.

In my solution, when the user clicks the submit button for a form, I check each control on the form (or whatever container is specified) and use reflection to determine if a validating method is defined for the control. If it is, the validation method is executed. If any of the validations fail, the routine returns a failure and allows the process to stop. This solution works well especially if you have several forms to validate.

References:
WinForm UI Validation
C# Validating input for textbox on winforms

Upvotes: 4

Mike Perrenoud
Mike Perrenoud

Reputation: 67918

They are listed there because they are inherited from the Control class. Here is Validated, and here is Validating. Note they are from Control.

Upvotes: 1

Nigel B
Nigel B

Reputation: 3597

You can use the validating event to cancel the action of the button if your criteria is not met and instead of putting that action in the onClick event place it in the validated event instead.

Upvotes: 2

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