Reflection How to Invoke Method with parameters

Question

I am trying to invoke a method via reflection with parameters and I get      object does not match target type   If I invoke a method without parameters  it works fine  Based on the following code if I call the method Test  TestNoParameters    it works fine  However if I call Test  Run    I get an exception  Is something wrong with my code   My initial purpose was to pass an array of objects e g  public void Run object   options  but this did not work and I tried something simpler e g  string without success      Assembly1 dll namespace TestAssembly       public class Main               public void Run string parameters                            Do something                       public void TestNoParameters                            Do something                           Executing Assembly exe public class TestReflection       public void Test string methodName                Assembly assembly   Assembly LoadFile     Assembly1 dll            Type type   assembly GetType  TestAssembly Main             if  type    null                        MethodInfo methodInfo   type GetMethod methodName                if  methodInfo    null                                object result   null                  ParameterInfo   parameters   methodInfo GetParameters                    object classInstance   Activator CreateInstance type  null                    if  parameters Length    0                                           This works fine                     result   methodInfo Invoke classInstance  null                                     else                                       object   parametersArray   new object      Hello                             The invoke does NOT work                         it throws  Object does not match target type                                   result   methodInfo Invoke methodInfo  parametersArray

User · Answer

Assembly assembly   Assembly LoadFile       bin Debug TestCases dll             get all types         var testTypes   from t in assembly GetTypes                           let attributes   t GetCustomAttributes typeof NUnit Framework TestFixtureAttribute   true                          where attributes    null  amp  amp  attributes Length  gt  0                         orderby t Name                         select t           foreach  var type in testTypes                          get test method in types              var testMethods   from m in type GetMethods                                 let attributes   m GetCustomAttributes typeof NUnit Framework TestAttribute   true                                where attributes    null  amp  amp  attributes Length  gt  0                               orderby m Name                               select m               foreach  var method in testMethods                                MethodInfo methodInfo   type GetMethod method Name                    if  methodInfo    null                                        object result   null                      ParameterInfo   parameters   methodInfo GetParameters                        object classInstance   Activator CreateInstance type  null                        if  parameters Length    0                                                   This works fine                         result   methodInfo Invoke classInstance  null                                             else                                               object   parametersArray   new object      Hello                                 The invoke does NOT work                             it throws  Object does not match target type                                       result   methodInfo Invoke classInstance  parametersArray

User · Answer

Change  methodInfo  to  classInstance   just like in the call with the null parameter array     result   methodInfo Invoke classInstance  parametersArray

User · Answer

A fundamental mistake is here   result   methodInfo Invoke methodInfo  parametersArray      You are invoking the method on an instance of MethodInfo  You need to pass in an instance of the type of object that you want to invoke on    result   methodInfo Invoke classInstance  parametersArray

User · Answer

I tried to work with all the suggested answers above but nothing seems to work for me  So i am trying to explain what worked for me here   I believe if you are calling some method like the Main below or even with a single parameter as in your question  you just have to change the type of parameter from string to object for this to work  I have a class like below    Assembly dll namespace TestAssembly      public class Main           public void Hello                          var name   Console ReadLine                Console WriteLine  Hello   called                Console WriteLine  Hello    name     at     DateTime Now                      public void Run string parameters                         Console WriteLine  Run   called                Console Write  You typed      parameters                      public string TestNoParameters                         Console WriteLine  TestNoParameters   called                return   TestNoParameters   called                       public void Execute object   parameters                         Console WriteLine  Execute   called               Console WriteLine  Number of parameters received       parameters Length               for int i 0 i lt parameters Length i                    Console WriteLine parameters i                                      Then you have to pass the parameterArray inside an object array like below while invoking it  The following method is what you need to work  private void ExecuteWithReflection string methodName object parameterObject   null        Assembly assembly   Assembly LoadFile  Assembly dll        Type typeInstance   assembly GetType  TestAssembly Main         if  typeInstance    null                MethodInfo methodInfo   typeInstance GetMethod methodName           ParameterInfo   parameterInfo   methodInfo GetParameters            object classInstance   Activator CreateInstance typeInstance  null            if  parameterInfo Length    0                           there is no parameter we can call with  null              var result   methodInfo Invoke classInstance  null                     else                       var result   methodInfo Invoke classInstance new object     parameterObject                          This method makes it easy to invoke the method  it can be called as following  ExecuteWithReflection  Hello    ExecuteWithReflection  Run   Vinod    ExecuteWithReflection  TestNoParameters    ExecuteWithReflection  Execute  new object    Vinod   Srivastav

User · Answer

I m invoking the weighted average through reflection  And had used method with more than one parameter   Class cls   Class forName propFile getProperty formulaTyp      reading class name from file  Object weightedobj   cls newInstance       invoke empty constructor  Class lt   gt    paramTypes     String class  BigDecimal   class  BigDecimal   class       3 parameter having first is method name and other two are values and their weight Method printDogMethod   weightedobj getClass   getMethod  applyFormula   paramTypes      created the object  return BigDecimal valueOf  Double  printDogMethod invoke weightedobj  formulaTyp  decimalnumber  weight    calling the method

User · Answer

The provided solution does not work for instances of types loaded from a remote assembly  To do that  here is a solution that works in all situations  which involves an explicit type re-mapping of the type returned through the CreateInstance call   This is how I need to create my classInstance  as it was located in a remote assembly      sample of my CreateInstance call with an explicit assembly reference object classInstance   Activator CreateInstance assemblyName  type FullName      However  even with the answer provided above  you d still get the same error  Here is how to go about      first  create a handle instead of the actual object ObjectHandle classInstanceHandle   Activator CreateInstance assemblyName  type FullName      unwrap the real slim-shady object classInstance   classInstanceHandle Unwrap        re-map the type to that of the object we retrieved type   classInstace GetType       Then do as the other users mentioned here

User · Answer

You have a bug right there  result   methodInfo Invoke methodInfo  parametersArray     it should be  result   methodInfo Invoke classInstance  parametersArray

User · Answer

I am posting this answer because many visitors enter here from google for this problem   string result   this GetType   GetMethod  quot Print quot   Invoke this  new object    quot firstParam quot   157   quot third Parammmm quot        when external  dll -instead of this GetType    you might use typeof YourClass

User · Answer

I would use it like this  its way shorter and it won t give any problems          dynamic result   null          if  methodInfo    null                        ParameterInfo   parameters   methodInfo GetParameters                object classInstance   Activator CreateInstance type  null               result   methodInfo Invoke classInstance  parameters Length    0   null   parametersArray

User · Answer

On  Net 4 7 2 to invoke a method inside a class loaded from an external assembly you can use the following code in VB net         Dim assembly As Reflection Assembly   Nothing         Try             assembly   Reflection Assembly LoadFile basePath  amp  AssemblyFileName              Dim typeIni   assembly  GetType  AssemblyNameSpace  amp   quot   quot   amp   quot nameOfClass quot               Dim iniClass   Activator CreateInstance typeIni  True              Dim methodInfo   typeIni GetMethod  quot nameOfMethod quot                 replace nothing by a parameter array if you need to pass var  paramenters             Dim parametersArray As Object     New Object                      without parameters is like this             Dim result   methodInfo Invoke iniClass  Nothing          Catch ex As Exception             MsgBox  quot Error initializing main layout  quot   amp  ex Message              Application Exit               Exit Sub         End Try

[c#] Reflection: How to Invoke Method with parameters

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