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Simple stuff, it seems like not possibile to cast long[] to object[]. Anyone knows why so?

What I have tried:

var array = (object[])Array.CreateInstance(typeof(long), 1);

System.InvalidCastException: Unable to cast object of type 'System.Int64[]' to type 'System.Object[]'.
Updated 27-Feb-21 9:04am
Gerry Schmitz 27-Feb-21 14:08pm
Array covariance doesn’t apply to value types.
csrss 27-Feb-21 14:27pm

1 solution

You can't cast an array of values to any other array type because value types are "special": they aren't all the same size, and value types can't be inherited anyway.

With reference types, the variable is always the same size: 8 bytes on a 64 bit system, 4 bytes on a 32 bit. Value types can be anything between 1 byte (normally padded to a machine word boundary) and ... well, there is no absolute limit, but I'd suspect a practical limit of under 2MB as that is the default stack size for a .NET app.

Since the size of the elements isn't the same, you can't cast the array to a different type without resizing the actual elements, and that means reallocating the array and creating a new type for each element, then copying the data over. That isn't going to happen!

It may help if you see this: Using struct and class - what's that all about?[^] - it may help you unerstand the difference!
csrss 27-Feb-21 15:07pm
Thx :)
OriginalGriff 27-Feb-21 16:21pm
You're welcome!

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