How to call a method from a dll using Reflection

Question

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dll file containing the method, Project file that calls the method in dll, exception and my findings are below, I do not understand what I'm missing. Please help!

dll file:

C#

public class Class2
    {
        public string TestMethod1()
        {
            return "hello world!";
        }

        public void TestMethod2(int test)
        {
        }
    }

Project where Method in dll is called:

C#

try
            {
                Assembly assembly = Assembly.LoadFrom(@"D:\TestDll.dll");                
                foreach (Type ti in assembly.GetTypes().Where(x => x.IsClass))
                {
                    if (ti.Name == "Class2")
                    {
                        ti.GetMethod("TestMethod2");
                        MethodInfo[] method = ti.GetMethods();
                        Type t = assembly.GetType("TestDll.Class2");
                        BindingFlags flags = BindingFlags.Public | BindingFlags.InvokeMethod | BindingFlags.Instance;
                        object res = t.InvokeMember("TestMethod2", BindingFlags.InvokeMethod, null, t, new object[0]);
                    }
                }
            }
            catch (Exception ex)
            {
                string msg = ex.Message;
            }

Exception:

MissingMethodException Occurred<br />
Method 'TestDll.Class2.TestMethod2' not found.

My Findings from MethodInfo:

method[1] = {Void TestMethod2(Int32)};<br /> method[1].Name = TestMethod2

If I change the last parameter i.e. input parameters following error occurs
Exception:

TargetException Occurred<br /> Object does not match target type.

Posted 10-Jan-14 0:27am

Prabhu S M

Updated 20-Nov-17 2:37am

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2 solutions

Solution 2

Simple: your methods are not static, they are instance methods: you need to create an instance of the object and pass that through, rather than trying to pass the type of the class, and you need to pass the argument through:

C#

Assembly assembly = Assembly.LoadFrom(@"D:\TestDll.dll");
foreach (Type ti in assembly.GetTypes().Where(x => x.IsClass))
    {
    if (ti.Name == "Class2")
        {
        Type t = assembly.GetType("TestDll.Class2");
        object obj = t.InvokeMember(null,
                                    BindingFlags.DeclaredOnly |
                                       BindingFlags.Public |
                                       BindingFlags.NonPublic |
                                       BindingFlags.Instance |
                                       BindingFlags.CreateInstance,
                                    null,
                                    null,
                                    null);
        object res = t.InvokeMember("TestMethod2", BindingFlags.InvokeMethod, null, obj, new object[] { (object)13 });
        }
    }

Posted 10-Jan-14 0:55am

OriginalGriff

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Karthik_Mahalingam · Accepted Answer · 2014-01-10T00:38:00

Solution 1

Try like this..

C#

if (ti.Name == "Class2")
           {
               MethodInfo TestMethod1 = ti.GetMethod("TestMethod1");
               MethodInfo TestMethod2 = ti.GetMethod("TestMethod2");
               var instance = Activator.CreateInstance(ti);
               string value = TestMethod1.Invoke(instance, null).ToString();
               TestMethod2.Invoke(instance, new object[] { 1 });

           }

Posted 10-Jan-14 0:38am

Karthik_Mahalingam

Comments

Prabhu S M 10-Jan-14 6:45am

Thanks Karthik! It's working, any idea how to invoke a method from an interface dll? I believe instance cannot be created for interface.

Karthik_Mahalingam 10-Jan-14 6:52am

welcome solomon :)
yes you can
check this link

Prabhu S M 10-Jan-14 7:10am

I don't understand it a bit Karthik :'(
can you explain using the code that I had given above.
Suppose Class2 class is implementing an Interface which has 2 methods and Class2 contains definition for both the methods declared in Interface i.e. TestMethod1 & TestMethod2.
How would I invoke the interface dll now?

Karthik_Mahalingam 10-Jan-14 7:17am

that is of no use, any how you should need the instance of the class implementing the interface...
so the interface will not comes to picture.
got it ??

Prabhu S M 13-Jan-14 2:29am

yes.. thanks Karthik!

Karthik_Mahalingam 13-Jan-14 3:45am

welcome :)

Member 11964881 21-Nov-17 1:54am

Thanks it worked. You can find detailed explanation of accessing properties and methods using reflection in C# here

Karthik_Mahalingam 21-Nov-17 2:08am

welcome