Convert value from string to generic type that is either Guid or int

Question

I've got a generic method which converts an id from a string (eg, retrieved from the Value of a HiddenField on an ASP.NET Form) to a target type and does something with it.

private void MyMethod<T>(string rawId, Action<T> doSomethingWithId)
{
    T id = (T)Convert.ChangeType(rawId, typeof(T));
    doSomethingWithId(id);
}

T will be either Guid or Int32 and the above code falls over (at runtime) when it is Guid, saying that the cast from String to Guid is invalid.

Then I thought I might try to check the type and if Guid, instantiate a new Guid:

var id = default(T);
if (id is Guid)
    id = new Guid(rawId);
else
    id = (T)Convert.ChangeType(rawId, typeof(T));

now this gives an error (at compile time) that Guid cannot be converted to type T

Not too sure how to work around this. Any suggestions?

Answer 1

the below code works fine with conversion to Guid . check it

id = (T)TypeDescriptor.GetConverter(typeof(T)).ConvertFromInvariantString(text);