Question

I am trying to make sure that user uses at least 6 characters as a password in my program.

I know how to set maximum size by using MaxLength, but how I do this for the minimum length?

Answer 1

Although competent_tech gives you my recommended approach, a primitive solution would be the following:

Drop a label on your form and give it an ErrorText.

Use the following code for your textbox KeyDown event:

protected override void OnLoad(object sender, EventArgs e)
{
    base.OnLoad(sender, e);

    txtPassword.KeyDown += OnPasswordKeydown;     
}

protected void OnPasswordKeydown(object sender, KeyEventArgs e)
{
    bool isValid = txtPassword.Text.Length < 6;

    ErrorText.Visible = isValid;
    AcceptButton.Visible = isValid;
}