Checking if field is null

Question

Do you need to use this to check if field is null in C# If (fieldName.Text ==  || fieldName.Text == null) If so what does each check check for or are they checking for the same thing?

Vulpes · Answer

You need to distinguish between a null string reference and an empty string. If you have this: string s = null; then it means that the variable 's' doesn't currently refer to a string instance. However if you have this: string s = ; it means that 's' does refer to a string instance but that instance has no characters i.e. it's an empty string. There is a convenience method that can be used to check for both: if (String.IsNullOrEmpty(fieldName.Text)) { // do something }