VB.Net Reflection Method Invoke returns null

Question

User-1962621908 posted

I need to access few private methods and members in the Microsoft.VisualStudio.Data.Tools.Package.dll . I did the following coding. everything works fine until the last code line.

Dim dte As EnvDTE.DTE
Dim configuration As EnvDTE.Configuration
Dim projectConfigProperties As Microsoft.VisualStudio.Data.Tools.Package.Project.Internal.ProjectConfigProperties

' Get the Assembly info 
Dim name As AssemblyName = New AssemblyName()
name.CodeBase = "file://C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\Extensions\Microsoft\SQLDB\Microsoft.VisualStudio.Data.Tools.Package.dll"
Dim dbProjectType As Type = assembly.GetType("Microsoft.VisualStudio.Data.Tools.Package.Project.DatabaseProjectPropertyValueType", True, True)
' Retrieve the enum info from the assembly 
Dim fields As FieldInfo() = dbProjectType.GetFields((BindingFlags.Public Or BindingFlags.Static Or BindingFlags.NonPublic))

Dim databaseProjectConfig As Microsoft.VisualStudio.Data.Tools.Package.Project.DatabaseProjectConfig
configuration = project.ConfigurationManager.ActiveConfiguration
projectConfigProperties = CType(configuration.Object, Microsoft.VisualStudio.Data.Tools.Package.Project.Internal.ProjectConfigProperties)
projectConfigObject = projectConfigProperties.GetType().GetProperty("ProjectConfig", System.Reflection.BindingFlags.NonPublic Or System.Reflection.BindingFlags.Instance).GetValue(projectConfigProperties)
databaseProjectConfig = CType(projectConfigObject, Microsoft.VisualStudio.Data.Tools.Package.Project.DatabaseProjectConfig)

Dim types As Type() = New Type() {GetType(String), GetType(Boolean), dbProjectType}
' Get method info 
Dim myMethod As MethodInfo = databaseProjectConfig.GetType().GetMethod("GetConfigurationProperty", BindingFlags.NonPublic Or BindingFlags.Instance, Nothing, types, Nothing)
' Invoke the method 
Dim val = myMethod.Invoke(projectConfigObject, New Object() {"SqlCommandVariablesFile", False, fields(0).GetValue(Nothing)})

The myMethod populates correctly. But when I try to invoke it, the val is always getting a null value. It would be great if someone can tell me where I went wrong.

Answer 1

User-271186128 posted

Hi priyalwalpita,

projectConfigObject = projectConfigProperties.GetType().GetProperty("ProjectConfig", System.Reflection.BindingFlags.NonPublic Or System.Reflection.BindingFlags.Instance).GetValue(projectConfigProperties)


Dim val = myMethod.Invoke(projectConfigObject, New Object() {"SqlCommandVariablesFile", False, fields(0).GetValue(Nothing)})

According to your code, it seems that you are invoke the property, instead of the methods. Please set a break point to check whether you set value for this property.

More details about using reflection, please refer to the following code:

Imports System
Imports System.Reflection

Public Class MagicClass
    Private magicBaseValue As Integer

    Public Sub New()
        magicBaseValue = 9
    End Sub

    Public Function ItsMagic(preMagic As Integer) As Integer
        Return preMagic * magicBaseValue
    End Function
End Class

Public Class TestMethodInfo
    Public Shared Sub Main()
        ' Get the constructor and create an instance of MagicClass

        Dim magicType As Type = Type.GetType("MagicClass")
        Dim magicConstructor As ConstructorInfo = magicType.GetConstructor(Type.EmptyTypes)
        Dim magicClassObject As Object = magicConstructor.Invoke(New Object(){})

        ' Get the ItsMagic method and invoke with a parameter value of 100

        Dim magicMethod As MethodInfo = magicType.GetMethod("ItsMagic")
        Dim magicValue As Object = magicMethod.Invoke(magicClassObject, New Object(){100})

        Console.WriteLine("MethodInfo.Invoke() Example" + vbNewLine)
        Console.WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue)
    End Sub
End Class

When invoke the method, you could also set a break point in the method to check the return data.

More details, see: https://msdn.microsoft.com/en-us/library/a89hcwhh(v=vs.110).aspx?cs-save-lang=1&cs-lang=vb#code-snippet-2

Best regards,
Dillion

Answer 2

User-1962621908 posted

Hi,

 I found the route cause in this problem when we are Invoking a method through reflection, we need to pass-in the exact matching param types in the Invoke method. That is why it was returned as null. After I passed in the exact same param types the method returned successfully. 

Following is the code I used and it worked. 

Setting up the type properties.

Dim fields As FieldInfo() = dbProjectType.GetFields((BindingFlags.Public Or BindingFlags.Static Or BindingFlags.NonPublic))

 '' Get Internal enum DatabaseProjectEventPropagation using reflection 
Dim dbeventPropagationType As Type = assembly.GetType("Microsoft.VisualStudio.Data.Tools.Package.Project.DatabaseProjectEventPropagation", True, True)
Dim dbEventPropgationFields As FieldInfo() = dbeventPropagationType.GetFields((BindingFlags.Public Or BindingFlags.Static Or BindingFlags.NonPublic))

Dim readTypes As Type() = New Type() {GetType(String), GetType(Boolean), dbProjectType}
 Dim writeTypes As Type() = New Type() {GetType(String), GetType(String), dbeventPropagationType, GetType(Microsoft.VisualStudio.Shell.Interop._PersistStorageType)}

Define the methods that we need to access via reflection 

projectConfigProperties = CType(configuration.Object, Microsoft.VisualStudio.Data.Tools.Package.Project.Internal.ProjectConfigProperties)
projectConfigObject = projectConfigProperties.GetType().GetProperty("ProjectConfig", System.Reflection.BindingFlags.NonPublic Or System.Reflection.BindingFlags.Instance).GetValue(projectConfigProperties)
databaseProjectConfig = CType(projectConfigObject, Microsoft.VisualStudio.Data.Tools.Package.Project.DatabaseProjectConfig)

Dim getPropertyMethod As MethodInfo = databaseProjectConfig.GetType().GetMethod("GetConfigurationProperty", BindingFlags.NonPublic Or BindingFlags.Instance, Nothing, readTypes, Nothing)
Dim setPropertyMethod As MethodInfo = databaseProjectConfig.GetType().GetMethod("SetConfigurationProperty", BindingFlags.NonPublic Or BindingFlags.Instance, Nothing, writeTypes, Nothing)

Invoking methods 

Dim val = getPropertyMethod.Invoke(projectConfigObject, New Object() {"AnsiNulls", False, fields(0).GetValue(Nothing)})
setPropertyMethod.Invoke(projectConfigObject, New Object() {"AnsiNulls", "False", dbEventPropgationFields(0).GetValue(Nothing), Microsoft.VisualStudio.Shell.Interop._PersistStorageType.PST_PROJECT_FILE})