validation of user input instantly when user leaves the text

hadoop hadoop

I want validation module to work when the user leaves the textbox or the textbox is out of focus. i.e. when the user input in one textbox and then focus on other textbox for input instantly error message should popup if the previous input is not valid.

Suppose ::

Username :: //txtUsername

Phone :: //txtPhone

here error message should popup instantly for txtName if it is invalid when txtName is out of focus.

I've develop a module for validation but it works when the form is complete,i.e. only at the save time.

#region "Input Validations"

private bool IsClientValid()

{

if (txtUsername.Text == string.Empty || txtUsername.Text == null)

{

MessageBox.Show("User Name is required", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

return false;

}

if (txtUsername.Text.Length > 200)

{

MessageBox.Show("User Name cannot be more than 200 characters", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

return false;

}

if (txtPhone.Text.Length > 20)

{

MessageBox.Show("Phone Number cannot be more than 20 characters", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

return false;

}

return true;

}

#endregion

4 Replies

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Manoj Bhoir11y ago

Accepted answer

Hi,

Just use LostFocus event to validate your code. Call your validation functions on TextBox LostFocus Event.

private void textBox1_LostFocus(object sender, System.EventArgs e) 	
{ 		
   if (IsClientValid() == false){
      //Show here Error Message.
   } 
}

hadoop hadoop11y ago
@Nanhe :: thanks for the reply. my application is desktop application how to set Autopostback property true for the textbox for desktop based application.
Nanhe Siddique11y ago
hi hadoop

First Set Autopostback property of textbox to true.
and then add this event handlar
protected void TextBox1_TextChanged(object sender, EventArgs e)
{
here write code whatever you want on textbox leave
}

i think it may help you

Manoj Bhoir11y ago

Hi,

When you change the focus by using the keyboard (TAB, SHIFT+TAB, and so on), by calling the Select or SelectNextControl methods, or by setting the ContainerControl.ActiveControl property to the current form, focus events occur in the following order:

Enter
GotFocus
Leave
Validating
Validated
LostFocus

When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order:

Enter
GotFocus
LostFocus
Leave
Validating
Validated

If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

If the Cancel property of the CancelEventArgs is set to true in the Validating event delegate, all events that would usually occur after the Validating event are suppressed.

The following code example demonstrates validating the text for TextBox1 :

private void textBox1_Validating(object sender, System.ComponentModel.CancelEventArgs e) 	
{ 		
// If nothing is entered,  		
// an ArgumentException is caught; if an invalid directory is entered,   		
// a DirectoryNotFoundException is caught. An appropriate error message   		
// is displayed in either case.  		
   try 		
   { 			
      System.IO.DirectoryInfo directory = new System.IO.DirectoryInfo(textBox1.Text); 			
      directory.GetFiles(); 			
      errorProvider1.SetError(textBox1, "");  		
   } 		
   catch(System.ArgumentException ex1) 		
   { 			
      errorProvider1.SetError(textBox1, "Please enter a directory");
   } 		
   catch(System.IO.DirectoryNotFoundException ex2) 		
   { 			
      errorProvider1.SetError(textBox1, "The directory does not exist." + "Try again with a different directory.");
   }  	
}  	
// This method handles the LostFocus event for textBox1 by setting the   	
// dialog's InitialDirectory property to the text in textBox1.  	
private void textBox1_LostFocus(object sender, System.EventArgs e) 	
{ 		
   openFileDialog1.InitialDirectory = textBox1.Text; 	
}  	
// This method demonstrates using the ErrorProvider.GetError method   	
// to check for an error before opening the dialog box.  	
private void button1_Click(System.Object sender, System.EventArgs e) 	
{ 		
//If there is no error, then open the dialog box.  		
   if (errorProvider1.GetError(textBox1)=="") 		
   { 			
      DialogResult dialogResult = openFileDialog1.ShowDialog(); 		
   } 	
}

For more details see this link :

https://msdn.microsoft.com/en-us/library/system.windows.forms.control.lostfocus%28v=vs.110%29.aspx