CODEWITHSUNDEEP
c#c#-4.0
mmg666
mmg666

Reputation: 353

ToString call on dynamic type variable behaves differently in C#

Can someone explain to me the difference between these two string variables :

        dynamic dateStrAsDynamic = "12/10/2013";
        var dateStrFromDynamic = dateStrAsDynamic.ToString();
        var regularDateStr = "12/10/2013";

These two behave exactly the same way but while debugging calling DateTime.Parse on the first one tells me that this dynamic operation is not supported while debugging, I mean "which dynamic operation?", whatever dynamic operation it is; must it not have been over?

The IL code generated by calling DateTime.Parse on those two (of course after ToString is called and assigned to dateStrFromDynamic) have a large difference as well that I am not able to grasp totally.

Do these two really have a difference, or am I missing something?

Upvotes: 3

Views: 1838

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1502286

I mean "which dynamic operation?"

The one that invokes a method using a dynamic variable as the argument.

Note that the type dateStrFromDynamic will still be dynamic - the compiler doesn't know that ToString() will definitely return a string. The result of almost any dynamic operation is another dynamic value - if you want to tell the compiler that you want the type of dateStrFromDynamic to be string, you need to make that explicit:

string dateStrFromDynamic = dateStrAsDynamic.ToString();

Or just:

string dateStrFromDynamic = dateStrAsDynamic;

(given that it really is a string to start with).

So yes, there is an enormous difference between dateStrFromDynamic and regularDateStr - and if you hover over var in Visual Studio, it will become more obvious as it will tell you the type that the compiler has inferred for each variable.

Upvotes: 8

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