explicit casting of object containing array - to an array

Question

The short version -

Is there an easy way to take a variable of type object containing an instance of an unknown array (UInt16[], string[], etc.) and treat it as an array, say call String.Join(",", obj) to produce a comma delimited string?

Trivial? I thought so too.

Consider the following:

object obj = properties.Current.Value;

obj might contain different instances - an array for example, say UInt16[], string[], etc.

I want to treat obj as the type that it is, namely - perform a cast to an unknown type. After I accomplish that, I will be able to continue normally, namely:

Type objType = obj.GetType();
string output = String.Join(",", (objType)obj);

The above code, of course, does not work (objType unknown).

Neither does this:

object[] objArr = (object[])obj;   (Unable to cast exception)

Just to be clear - I am not trying to convert the object to an array (it's already an instance of an array), just be able to treat it as one.

Thank you.

Maybe you can replace object obj = properties.Current.Value; by dynamic obj = properties.Current.Value; then treat obj as an array? — Guillaume
– Guillaume, Commented Dec 13, 2012 at 8:34

Jon Skeet · Accepted Answer · 2012-12-13 08:34:16Z

9

Assuming you're using .NET 4 (where string.Join gained more overloads) or later there are two simple options:

Use dynamic typing to get the compiler to work out the generic type argument:

dynamic obj = properties.Current.Value;
string output = string.Join(",", obj);

Cast to IEnumerable, then use Cast<object> to get an IEnumerable<object>:

IEnumerable obj = (IEnumerable) properties.Current.Value;
string output = string.Join(",", obj.Cast<object>());

answered Dec 13, 2012 at 8:34

Jon Skeet

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zulfik Over a year ago

You are my god! Thank you :-)

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