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Possible Duplicate:
How to check if String is null

I need to be able to check for a null value, only, inside a string. The best method I am currently aware of is String.IsNullOrEmpty(), which does not fit what we are trying to do (string.empty values are allowed, nulls are not). Does anyone have any suggestions?

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NealR
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4 Answers4

12

just compare your string to null

bool stringIsNull = mystring == null;

here's an extension method for you

public static class ExtensionMethods
{
    public static bool IsNull(this string str)
    {
        return str == null;
    }
}
Sam I am says Reinstate Monica
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  • Won't this throw an error if mystring actually is null? – NealR Jan 07 '13 at 22:00
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    @NealR No, it won't, it will just return `true`. – Servy Jan 07 '13 at 22:01
  • @NealR No, it's evaluating `mystring == null` and then setting `stringIsNull` to that value. To make it more explicit: `bool stringIsNull = (mystring == null)` – Ally Jan 07 '13 at 22:06
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    @NealR Extension methods are really just static methods. So in the case of this extension method: `string a = null; a.IsNull() // true - no exception thrown` is just really doing `string a = null; ExtensionMethods.IsNull(a)` – RobH Jan 07 '13 at 22:24
5

You check the same way you check if any other variable is null:

if(variable == null)
{
  //do stuff
}
Servy
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3

If you want to skip null values, simply use != null:

if(str != null)
{

}
Tim Schmelter
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2
if (variable != null) 
 //do your action for not null
else 
  //variable is null
apollosoftware.org
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