How to check if String is null

Question

I am wondering if there is a special method trick to check if a String object is null  I know about the String IsNullOrEmpty method but I want to differentiate a null String from an empty String         Should I simply use   if  s    null           blah blah           or is there another way

User · Answer

You can use the null coalescing double question marks to test for nulls in a string or other nullable value type:

textBox1.Text = s ?? "Is null";

The operator '??' asks if the value of 's' is null and if not it returns 's'; if it is null it returns the value on the right of the operator.

More info here: https://msdn.microsoft.com/en-us/library/ms173224.aspx

And also worth noting there's a null-conditional operator ?. and ?[ introduced in C# 6.0 (and VB) in VS2015

textBox1.Text = customer?.orders?[0].description ?? "n/a";

This returns "n/a" if description is null, or if the order is null, or if the customer is null, else it returns the value of description.

More info here: https://msdn.microsoft.com/en-us/library/dn986595.aspx

User · Answer

You can check with null or Number   First  add a reference to Microsoft VisualBasic in your application   Then  use the following code   bool b   Microsoft VisualBasic Information IsNumeric  null    bool c   Microsoft VisualBasic Information IsNumeric  abc      In the above  b and c should both be false

User · Answer

An object can t be null - the value of an expression can be null  It s worth making the difference clear in your mind  The value of s isn t an object - it s a reference  which is either null or refers to an object   And yes  you should just use  if  s    null    Note that this will still use the overloaded    operator defined in string  but that will do the right thing

User · Answer

To sure  you should use function to check is null and empty as below   string str       if   String IsNullOrEmpty str

[c#] How to check if String is null

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