使用反射来调用函数 [英] Using reflection to call functions

问题描述

我想调用一个函数，该函数使用用户提供的变量返回布尔值但无效...这里是代码

I want to call a function which returns boolean using a variable supplied by the user but to no avail ... Here''s the code

Try
    Dim ass As Assembly = Assembly.LoadFile(Application.StartupPath & "\ReflectionLib.dll")
    Dim t_sam As Type = ass.GetType("ReflectionLib")
    Dim hh_m As MethodInfo = t_sam.GetMethod("ShowX", BindingFlags.Public Or BindingFlags.Static)
    hh_m.Invoke(Nothing, New Object() {})
Catch ex As Exception
    MessageBox.Show(ex.Message + ex.StackTrace + vbLf)
End Try

我继续对象引用没有设置为对象错误的实例使用此代码

I keep getting Object reference not set to an instance of object error with this code

hh_m.Invoke(Nothing, New Object() {})

推荐答案

在您发布的代码中将断点放在第1行并逐步使用F10。查看哪个对象为null并找出原因。

Put breakpoint at line 1 in code you posted and step through using F10. See which object is null and figure out why.

以下代码解决了我对该方法的调用问题的解决方法...我继续得到我的类型实际上是null的错误，所以我浏览了旧帖子并发现了这个解决方案，虽然它必须稍微调整一下以满足我的需求它工作正常。感谢您宝贵的意见我很期待与您合作





Imports System.Reflection



公共类Form1



私有asm As System.Reflection.Assembly

私有t作为类型（）

私有类型

私有m作为MethodInfo（）

私有mm作为MethodInfo



Private Sub Form1_Load（ByVal sender As System.Object，ByVal e As System.EventArgs）Handles MyBase.Load

''这里我们必须加载classlibrary的程序集givig我们的完整路径classLibrary.dll



asm = System.Reflection.Assembly.LoadFrom（Environment.CurrentDirectory +\ dll\ReflectionLib.dll）

End Sub



Private Sub Button1_Click（ByVal sender As System.Object，ByVal e As System.EventArgs）处理Button1.Click

t = asm.GetTypes（）

F.或者我作为整数= 0到t.Length - 1

ListBox1.Items.Add（t（i）.FullName）

下一页我

结束Sub



Private Sub Button2_Click（ByVal sender As System.Object，ByVal e As System.EventArgs）处理Button2.Click

mm = ty.GetMethod（ListBox2.SelectedItem.ToString（））

Dim o As Object

o = Activator.CreateInstance（ty）

Dim oo As Object（）= {Int32.Parse（TextBox1.Text），Int32.Parse（TextBox2.Text）}

''如果方法中没有参数那么在oo的位置传递null



TextBox3.Text = mm.Invoke（o，oo）.ToString（）

End Sub



Private Sub ListBox1_SelectedIndexChanged（ByVal sender As System.Object，ByVal e As System.EventArgs）Handles ListBox1.SelectedIndexChanged

ListBox2.Items.Clear（）

ty = asm.GetType（ListBox1.SelectedItem.ToStr ing（））

m = ty.GetMethods（）

对于j As Integer = 0到m.Length - 1

ListBox2.Items。添加（m（j）.Name）

下一页j

结束子

The following code solved my hick up concerning the Invocation of the method... I kept on getting the error that my type was in fact null, so I browsed on old posts and found this solution, though it has to be tweaked a little to suit my needs it works fine. thanks for your valued input I look forward to working with you soon


Imports System.Reflection

Public Class Form1

Private asm As System.Reflection.Assembly
Private t As Type()
Private ty As Type
Private m As MethodInfo()
Private mm As MethodInfo

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
''Here wec have to load the assembly of classlibrary by givig the full path of our classLibrary.dll

asm = System.Reflection.Assembly.LoadFrom(Environment.CurrentDirectory + "\dll\ReflectionLib.dll")
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
t = asm.GetTypes()
For i As Integer = 0 To t.Length - 1
ListBox1.Items.Add(t(i).FullName)
Next i
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
mm = ty.GetMethod(ListBox2.SelectedItem.ToString())
Dim o As Object
o = Activator.CreateInstance(ty)
Dim oo As Object() = {Int32.Parse(TextBox1.Text), Int32.Parse(TextBox2.Text)}
''If there is no parameter in method then on the place of oo pass the null

TextBox3.Text = mm.Invoke(o, oo).ToString()
End Sub

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
ListBox2.Items.Clear()
ty = asm.GetType(ListBox1.SelectedItem.ToString())
m = ty.GetMethods()
For j As Integer = 0 To m.Length - 1
ListBox2.Items.Add(m(j).Name)
Next j
End Sub

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