c# casting to type gotten from typename as string

Question

I want to work around the fact that my WCF servicelayer can not handle a generic method like this:

public void SaveOrUpdateDomainObject<T>(T domainObject)
{     
    domainRoot.SaveDomainObject<T>(domainObject);
}

so I built this workaround method instead

public void SaveOrUpdateDomainObject(object domainObject, string typeName)
{     
    Type T = Type.GetType(typeName);
    var o = (typeof(T))domainObject;
    domainRoot.SaveDomainObject<typeof(T)>(o);
}

The problem is this does not compile somehow.

I think this is the result of me not fully understanding the difference between

• Type T I believe this is an object of type "Type"

• the result of typeof(T) I believe this results in a non-object type version of the type of T (I don't know how to say this exactly)

Answer 1

You don't need typeName: you have to either pass around Type instances, or use object.GetType() to retrieve object run-time type.

In either case,

MethodInfo genericSaveMethod = domainRoot.GetType().GetMethod("SaveDomainObject");
MethodInfo closedSaveMethod = genericSaveMethod .MakeGenericMethod(domainObject.GetType());
closedSaveMethod.Invoke(domainRoot, new object[] { domainObject });

Answer 2

Unfortunately, something like this is quite hard in C#. It's easy to get the correct Type instance from a string, just like you did, but you'll have to use reflection to get the right method.

Try something along the lines of

public void SaveOrUpdateDomainObject(object domainObject, string typeName)
{
    Type T = Type.GetType(typeName);
    MethodInfo genericMethod = domainRoot.GetType().GetMethod("SaveDomainObject");
    MethodInfo method = genericMethod.MakeGenericMethod(T);
    method.Invoke(domainRoot, new object[] { domainObject });
}

Answer 3

I think I had a similar problem, however did this which is a bit messy:

if (businessObject is Made4Print.Country) ((Made4Print.Country)businessObject).Save(); else if (businessObject is Made4Print.User) ((Made4Print.User)businessObject).Save();

... Loads of others...

else if (businessObject is Made4Print.Timezone) ((Made4Print.Timezone)businessObject).Save();

Will be interested in a better solution.