difference between string.empty and isNullOrEmpty?

Question

I have the following short piece of code that is never returning the string "selected".

Protected Function SelectedType(ByVal val As String) As String
    If val <> String.Empty Then Return "selected"
End Function

However, if I change it to this, it works. Is there anything wrong when my shorthand code above? -Thanks

Protected Function SelectedType(ByVal val As String) As String
    If Not String.IsNullOrEmpty(val) Then
        Return "selected"
    End If
End Function

Stephane Delcroix · Accepted Answer · 2013-03-14 15:50:36Z

4

String.Empty is "", null is Nothing.

you can compare if a string is null, if it's empty, or both at the same time with IsNullOrEmpty ()

edited Mar 14, 2013 at 15:50

answered Mar 14, 2013 at 15:44

Stephane Delcroix

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3 Comments

SkyeBoniwell Over a year ago

so: If Not String.IsNullOrEmpty(val) Then Return "selected"?

SkyeBoniwell Over a year ago

btw I'm trying to keep it on a single line

Stephane Delcroix Over a year ago

yes, that's correct. val is probably Nothing that's why the first code never returns "selected"

Reed Copsey · Accepted Answer · 2013-03-14 15:48:53Z

3

When you call If Not String.IsNullOrEmpty(val) Then, you're checking to see if the value is equal to String.Empty or if the value is equal to Nothing.

This would be more like writing your first example as:

Protected Function SelectedType(ByVal val As String) As String
    If val <> Nothing And val <> String.Empty Then 
        Return "selected"
    End If
End Function

answered Mar 14, 2013 at 15:48

Reed Copsey

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Comments

Aghilas Yakoub · Accepted Answer · 2013-03-14 15:44:01Z

1

IsNullOrEmpty offers additional security against null values, where otherwise your code would fail

answered Mar 14, 2013 at 15:44

Aghilas Yakoub

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