The ErrorProvider control is quite useful when it comes to user input validation. The next code segment assumes an ErrorProvider control named errorProvider1 has been placed on a form along with a Textbox named usernameTextBox and a ComboBox named comboBox1.
private void usernameTextbox_Leave(object sender, EventArgs e)
{
if (String.IsNullOrEmpty(usernameTextbox.Text))
{
errorProvider1.SetError(usernameTextbox, "enter a value"); //Check For Empty Strings
}
else
{
if (usernameTextbox.Text.All(char.IsDigit))
{
errorProvider1.SetError(usernameTextbox, "enter a string value!"); //Check for Numbers
}
else
{
if (usernameTextbox.Text.Length 8)
{
errorProvider1.SetError(usernameTextbox, "can only be 8 characters long"); //Check Length
}
}
}
}
private void comboBox1_Leave(object sender, EventArgs e)
{
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (int.Parse(comboBox1.SelectedItem.ToString()) {
errorProvider1.SetError(usernameTextbox, "can only be 18 and above"); //Determine Selection
}
}