convert Null Value from convert.tostring()

Question

I have code like this.

string b=null;
string a = Convert.ToString(b);

Ref from:

Checking for null before ToString()

But while i convert b to string i get only null value not empty string.but some days ago i have also done null coversion using same convert.tostring(). at that it works fine but now not working. i am rotating my head here and there pls help me why this is happening? only thing is that i worked in 3.5 framework but now 4.0 .

Answer 1

Convert.ToString(string) will return the string unchanged. This is true of every version of the framework, as per the documentation:

• 4.0
• 3.5
• 3.0
• 2.0

You are mistaken that calling Convert.ToString((string)null) ever returned anything except null. What you were probably calling was Convert.ToString((object)null). This will return empty-string.

string a = Convert.ToString((object)null);
string b = Convert.ToString((string)null);
// a now equals string.Empty, but b equals null.

You could cast string b to an object as I have done, but I would suggest you use the null-coalescing operator instead:

string a = b ?? string.Empty