How Should Validate DropDown Box And Textbox

i have been using required field validator to validate textbox and dropdown box in asp.net .. how should i validate this dropdownbox and textbox . i simple want if textbox is blank . it needs to show error message . and if all is ok . then it validate .[Code]

Code:
public bool checkinput() {
if (TxtName.Text == ""){
RequiredFieldValidator1.ErrorMessage = "User Name cannot be blank";
return false;
}
if (TxtMobile.Text == "") {
RequiredFieldValidator2.ErrorMessage = "Mobile no cannot be blank";

[code]...