Unable to cast object of type 'System.Linq.OrderedEnumerable`2[***]' to type 'System.Collections.Generic.IEnumerable`1[***]'

Question

I have an object DirectoryToken that inherits from the class Token. In my code I have a GetValues method which takes a list of tokens, and puts together the value for each item in the list based on the information contained in the token object.

//NameTokens is an object of type **List<DirectoryToken>**
List<String> PathValues = GetValues((IEnumerable<Token>)settings.DirectoryDefinition.**NameTokens**.OrderBy(x => x.Index));


private List<String> GetReportValues(IEnumerable<Token> TokenList)
{

}

What I notice is when I run the code on one machine (Windows 7, .NET 3.5), it runs fine. However, when I move the built msi to another machine and try to run the same test, I get the following error message.

Unable to cast object of type 'System.Linq.OrderedEnumerable2[DirectoryToken,System.Int32]' to type 'System.Collections.Generic.IEnumerable1[Token]'.

I don't think changing the code is the right way to attack this issue. Any suggestions what this problem could be from and maybe what version I can update my 3.5 to, to remedy this?

Solution 1

You're trying to convert a collection of DirectoryToken to a collection of Token.

This is called a covariant conversion, and it's only supported in .Net 4.0 or later.

If you can't upgrade, you can call .Cast<Token>() to create a new IEnumerable<T> instance (actually an iterator) that casts each object to the desired type.

Under no circumstances do you need an explicit cast operation.

Solution 2

Right, not quite there yet.

List<String> PathValues = GetValues(settings.DirectoryDefinition.NameTokens.OrderBy(x => x.Index).Cast<Token>()); 

will work.

This is because although DirectoryToken is a Token, IEnumerable<DirectoryToken> is NOT an IEnumerable<Token>. You can't just cast directly do that.