Question

Say I need to satisfy if else statement that

1. CustomerCode must be filled in(not null)
2. CustomerCode must be dataType varchar

How to write if else correctly?
Thanks for any help in advanced, guys!

sqlCustomerMaster.InsertParameters["CustomerCode"].DefaultValue =
                                                txtCustomerCode.Text.ToString();
try
{
    txtCustomerCode.Text = "";
    if (txtCustomerCode.Text != null)
    {
        sqlCustomerMaster.Insert();
    }
    else
    {
    }
}

Answer 1

Since the input is from a text box there always should be a mapping to varchar, so you just want to check whether the string is null or empty:

if (!string.IsNullOrEmpty(txtCustomerCode.Text))
{
    sqlCustomerMaster.Insert();
}

This will guarantee txtCustomerCode.Text has at least one character but not whether its numeric etc, but you did not list any other conditions.