C# dynamic object initializer won't compile

Question

The following code seems reasonable to me. It should create the object and then use the dynamic features to let me assign any properties I like. However the compiler says that "ExpandoObject does not contain a definition for Test". To which I say, "I know, that's the freaking point!"

dynamic example = new ExpandoObject
{
  Test = "fail"
};

Any ideas why csc isn't allowing this.

The alternative is to manually expand the code into individual property assignments.

dynamic example = new ExpandoObject();
example.Test = "fail";

Which is annoying when I have lots of properties to assign.

Please vote for this feature in Visual Studio UserVoice.

orad
– orad

2015-02-06 20:29:11 +00:00
Commented Feb 6, 2015 at 20:29 — orad
– orad, Commented Feb 6, 2015 at 20:29

Kirk Woll · Accepted Answer · 2010-11-18 15:18:16Z

13

Within the object initializer, the type is ExpandoObject, not dynamic, so you don't get dynamic functionality. After the initializer, you are operating on a variable of type dynamic and so dynamic functionality is available there.

answered Nov 18, 2010 at 15:18

Kirk Woll

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1 Comment

Andrew Davey Over a year ago

Ah, yes that makes sense. The object initializer expression is not typed as dynamic.

Judah Gabriel Himango · Accepted Answer · 2010-11-18 15:18:56Z

7

In your first example, the C# compiler will look for a property named Test on the ExpandoObject. It doesn't exist.

In your second example, the compiler will look for a Test property on a dynamic object. This is allowed, so it compiles.

answered Nov 18, 2010 at 15:18

Judah Gabriel Himango

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