I would like to use a customvalidator control to handle all my validation, but I can't figure out how to set the error message in the code-behind for different checks. Is this possible?
You can set the error message in the OnServerValidate method as you wish based on your validation logic:
protected void customValidator1_Validate(object sender, ServerValidateEventArgs e)
{
if (e.Value.Length < 5)
{
e.IsValid = true;
}
else
{
customValidator1.ErrorMessage = "Length must be less than 5.";
e.IsValid = false;
}
}