Textbox validation in a Windows Form

in NET4.0 there is a nice function

 if(string.IsNullOrWhiteSpace(textBox1.Text))
{
   //raise your validation exception
}
else {
  //go to submit
}

You can make your own custom validation function. This may be very naive, but somehow it will work.

private bool WithErrors()
{
    if(textBox1.Text.Trim() == String.Empty) 
        return true; // Returns true if no input or only space is found
    if(textBox2.Text.Trim() == String.Empty)
        return true;
    // Other textBoxes.

    return false;
}

private void buttonSubmit_Click(object sender, EventArgs e)
{
    if(WithErrors())
    {
        // Notify user for error.
    }
    else
    {
        // Do whatever here... Submit
    }
}

It can be easily be done using error provider here is the code.Error Provider you can find in your toolbox.

    private void btnsubmit_Click(object sender, EventArgs e)
            {

                if (string.IsNullOrEmpty(txtname.Text))
                {

                    txtname.Focus();
                    errorProvider1.SetError(txtname, "Please Enter User Name");
                }

                if (string.IsNullOrEmpty(txtroll.Text)) {
                    txtroll.Focus();
                    errorProvider1.SetError(txtroll, "Please Enter Student Roll NO");
                }
}

Here is output image