Best C# method for checking for a null string value [duplicate]

Question

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?

you should check this out stackoverflow.com/questions/7553567/… — Daniel Figueroa
– Daniel Figueroa, Commented Jan 7, 2013 at 22:02
@DJKRAZE: OP has explained that, because String.Empty is ok whereas null is not. — Tim Schmelter
– Tim Schmelter, Commented Jan 7, 2013 at 22:11

Sam I am says Reinstate Monica · Accepted Answer · 2013-01-07 22:18:47Z

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;
    }
}

edited Jan 7, 2013 at 22:18

answered Jan 7, 2013 at 22:00

Sam I am says Reinstate Monica

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4 Comments

NealR Over a year ago

Won't this throw an error if mystring actually is null?

Servy Over a year ago

@NealR No, it won't, it will just return true.

Ally Over a year ago

@NealR No, it's evaluating mystring == null and then setting stringIsNull to that value. To make it more explicit: bool stringIsNull = (mystring == null)

RobH Over a year ago

@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)

Servy · Accepted Answer · 2013-01-07 22:00:20Z

5

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

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

answered Jan 7, 2013 at 22:00

Servy

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Comments

Tim Schmelter · Accepted Answer · 2013-01-07 22:00:33Z

3

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

if(str != null)
{

}

answered Jan 7, 2013 at 22:00

Tim Schmelter

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Comments

C0L.PAN1C · Accepted Answer · 2013-01-07 22:01:40Z

2

if (variable != null) 
 //do your action for not null
else 
  //variable is null

answered Jan 7, 2013 at 22:01

C0L.PAN1C

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