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All, I have a method that is currently used to invoke DLLs of return type bool, this works great. This method is
public static bool InvokeDLL(string strDllName, string strNameSpace,
string strClassName, string strMethodName,
ref object[] parameters,
ref string strInformation,
bool bWarnings = false)
{
try
{
// Check if user has access to requested .dll.
if (!File.Exists(Path.GetFullPath(strDllName)))
{
strInformation = String.Format("Cannot locate file '{0}'!",
Path.GetFullPath(strDllName));
return false;
}
else
{
// Execute the method from the requested .dll using reflection.
Assembly DLL = Assembly.LoadFrom(Path.GetFullPath(strDllName));
Type classType = DLL.GetType(String.Format("{0}.{1}",
strNameSpace, strClassName));
if (classType != null)
{
object classInstance = Activator.CreateInstance(classType);
MethodInfo methodInfo = classType.GetMethod(strMethodName);
if (methodInfo != null)
{
object result = null;
result = methodInfo.Invoke(classInstance, new object[] { parameters });
return Convert.ToBoolean(result);
}
}
// Invocation failed fatally.
strInformation = String.Format("Could not invoke the requested DLL '{0}'! " +
"Please insure that you have specified the namespace, class name " +
"method and respective parameters correctly!",
Path.GetFullPath(strDllName));
return false;
}
}
catch (Exception eX)
{
strInformation = String.Format("DLL Error: {0}!", eX.Message);
if (bWarnings)
Utils.ErrMsg(eX.Message);
return false;
}
}
Now, I want to extend this method so that I can retrieve return values from a DLL of any type. I planned to do this using generics but immediately have gone into territory unknown to me. How do I return T when it is unknown at compile time, I have looked at reflection but I am unsure how it would be used in this case. Take the first check in the above code
public static T InvokeDLL<T>(string strDllName, string strNameSpace,
string strClassName, string strMethodName,
ref object[] parameters, ref string strInformation,
bool bWarnings = false)
{
try
{
// Check if user has access to requested .dll.
if (!File.Exists(Path.GetFullPath(strDllName)))
{
strInformation = String.Format("Cannot locate file '{0}'!",
Path.GetFullPath(strDllName));
return "WHAT/HOW??";
...
How can I achieve what I want, or shall I just overload the method?
Thanks very much for your help.
220
What are generic methods in Java? Similar to generic classes you can also define generic methods in Java. These methods use their own type parameters. Just like local variables, the scope of the type parameters of the methods lies within the method.
A generic method's body is declared like that of any other method. Note that type parameters can represent only reference types, not primitive types (like int, double and char). Following example illustrates how we can print an array of different type using a single Generic method −
You can have two generic type parameters of the different type as shown below. We can specify the restrictions on the types of parameters using the where clause. A compile-time error is generated when you call your generic method with the wrong types The Value type like int, float, struct etc. must be used as the parameter
It is exactly like a normal function, however, a generic method has type parameters that are cited by actual type. This allows the generic method to be used in a more general way. The compiler takes care of the type of safety which enables programmers to code easily since they do not have to perform long, individual type castings.
Replace
return false;
by
return default(T);
and
return Convert.ToBoolean(result);
by
return (T)result;
When you've not got a real value from the DLL, you obviously have to create a value from somewhere. The only way that works for every possible type T is return default(T) which gives whatever the default value for that type is (i.e. 0 for int, null for any reference type).
If you place type constraints on the type parameter you can get more options, but at the expense of genericity.
44
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