Using Case/Switch and GetType to determine the object

Sem_Dendoncker_29964 0
Viewed 298649

Possible Duplicate:
C# - Is there a better alternative than this to ‘switch on type’?

If you want to switch on a type of object, what is the best way to do this?

Code snippet

private int GetNodeType(NodeDTO node)
{
    switch (node.GetType())
    { 
        case typeof(CasusNodeDTO):
            return 1;
        case typeof(BucketNodeDTO):
            return 3;
        case typeof(BranchNodeDTO):
            return 0;
        case typeof(LeafNodeDTO):
            return 2;
        default:
            return -1;
    }
}

I know this doesn't work that way, but I was wondering how you could solve this. Is an if/else statement appropriate in this case?

Or do you use the switch and add .ToString() to the type?

case switch-statement reflection .net c#
10 Answers

This won't directly solve your problem as you want to switch on your own user-defined types, but for the benefit of others who only want to switch on built-in types, you can use the TypeCode enumeration:

switch (Type.GetTypeCode(node.GetType()))
{
    case TypeCode.Decimal:
        // Handle Decimal
        break;

    case TypeCode.Int32:
        // Handle Int32
        break;
     ...
}
user_555590

If I really had to switch on type of object, I'd use .ToString(). However, I would avoid it at all costs: IDictionary<Type, int> will do much better, visitor might be an overkill but otherwise it is still a perfectly fine solution.

user_601880

I'd just use an if statement. In this case: 

Type nodeType = node.GetType();
if (nodeType == typeof(CasusNodeDTO))
{
}
else ...

The other way to do this is:

if (node is CasusNodeDTO)
{
}
else ...

The first example is true for exact types only, where the latter checks for inheritance too.

user_4890

You can do this:

if (node is CasusNodeDTO)
{
    ...
}
else if (node is BucketNodeDTO)
{
    ...
}
...

While that would be more elegant, it's possibly not as efficient as some of the other answers here.

user_4558740

One approach is to add a pure virtual GetNodeType() method to NodeDTO and override it in the descendants so that each descendant returns actual type.

user_574280

Depending on what you are doing in the switch statement, the correct answer is polymorphism. Just put a virtual function in the interface/base class and override for each node type.

user_564720
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