Question

Is there a way to cast a dictionary i a one-liner and without all the overhead in C# .net 3?

var result = new Dictionary<string, AccessoryVariant>();
foreach (BaseVariant variant in mVariants.Values)
{
    result.Add(variant.Id, (AccessoryVariant)variant);
}
return result;

I would like to do something like this:

return (Dictionary<string, AccessoryVariant>)mVariants;

/Sven

Answer 1

Assuming you’re using .NET 3.5 or 4, you can use the ToDictionary method in LINQ:

return mVariants.Values.ToDictionary(v => v.Id, v => (AccessoryVariant) v);

Alternatively:

return mVariants.Values.Cast<AccessoryVariant>().ToDictionary(v => v.Id);

Or (assuming mVariants is already using the Id as the key):

return mVariants.ToDictionary(pair => pair.Key,
                              pair => (AccessoryVariant) pair.Value);

Note that you can’t cast the dictionary directly, because assuming mVariant is a Dictionary<string, BaseVariant>, someone could add a non-AccessoryVariant to the dictionary as a value, which would clearly mess up any code which (reasonably) assumed that the Dictionary<string, AccessoryVariant> only contained AccessoryVariant values.