How to reflection using ASP.NET 2.0 and VB.NET

This tutorial demonstrates how to go get class's property value and invoke class's method with Reflection.

This tutorial demonstrates how to go get class's property value and invoke class's method with Reflection.

Reflection provides objects (of type Type) that encapsulate assemblies, modules and types. You can use reflection to dynamically create an instance of a type, bind the type to an existing object, or get the type from an existing object and invoke its methods or access its fields and properties. If you are using attributes in your code, Reflection enables you to access them.
First, you will need to import the System. Reflection namespace

Imports System.Reflection;

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The System.Reflection namespace contains classes and interfaces that provide a managed view of loaded types, methods, and fields, with the ability to dynamically create and invoke types.
We use btnGetProperty_Click to get the property value of the class InstanceClass. And we use btnInvoke_Click to invoke the function getFunction of the class InstanceClass. The code as follows.

Protected Function getObjectProperty(ByVal str As String) As String Dim retValue As String = "" Try Dim o As Object = Activator.CreateInstance(type, New Object() {Me.txtPropertyValue.Text.Trim()}) Dim pi As PropertyInfo = type.GetProperty("ReturnValue", GetType(String)) retValue = pi.GetValue(o, Nothing).ToString() Catch ex As Exception Console.WriteLine(ex.Message) End Try Return retValue End Function Protected Function getOjbectMethod(ByVal str As String) As String Dim retValue As Object = Nothing Try Dim o As Object = Activator.CreateInstance(type) Dim mi As MethodInfo = type.GetMethod("getFunction", BindingFlags.Public Or BindingFlags.Instance, Nothing, New Type() {GetType(String)}, Nothing) retValue = mi.Invoke(o, New Object() {str}) Catch ex As Exception Console.WriteLine(ex.Message) End Try Return retValue.ToString() End Function Protected Sub btnGetProperty_Click(ByVal sender As Object, ByVal e As EventArgs) Me.lblPropertyResult.Text = Me.getObjectProperty(Me.txtPropertyValue.Text.Trim()) End Sub Protected Sub btnInvoke_Click(ByVal sender As Object, ByVal e As EventArgs) Me.lblInvokeResult.Text = Me.getOjbectMethod(Me.txtParameter.Text.Trim()) End Sub

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Add one custom class InstanceClass in this example.The code as follows:

Imports System Imports System.Data Imports System.Configuration Imports System.Web Imports System.Web.Security Imports System.Web.UI Imports System.Web.UI.WebControls Imports System.Web.UI.WebControls.WebParts Imports System.Web.UI.HtmlControls Public Class InstanceClass Private _returnValue As String = "" Public Property ReturnValue() As String Get Return "You input value is:" + _returnValue End Get Set(ByVal value As String) _returnValue = value End Set End Property Public Sub New() End Sub Public Sub New(ByVal str As String) Me._returnValue = str End Sub Public Function getFunction(ByVal str As String) As String Return "You input value is:" + str End Function End Class

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The front end ReflectionCsharp.aspx page looks something like this:

<table style="width: 708px"> <tr> <td style="width: 68px">PropertyValue:</td> <td style="width: 100px"> <asp:TextBox ID="txtPropertyValue" runat="server"></asp:TextBox></td> <td style="width: 53px">MethodParameter:</td> <td style="width: 100px"> <asp:TextBox ID="txtParameter" runat="server"></asp:TextBox></td> </tr> <tr> <td colspan="2"> <asp:Button ID="btnGetProperty" runat="server" OnClick="btnGetProperty_Click" Text="GetPropertyValue" /></td> <td colspan="2"> <asp:Button ID="btnInvoke" runat="server" OnClick="btnInvoke_Click" Text="InvokeMethod" /></td> </tr> <tr> <td style="width: 68px; height: 21px">Result:</td> <td style="width: 100px; height: 21px; text-align: left;"> <asp:Label ID="lblPropertyResult" runat="server" ForeColor="Red" Width="258px"></asp:Label></td> <td style="width: 53px; height: 21px">Result:</td> <td style="width: 100px; height: 21px;text-align: left;"> <asp:Label ID="lblInvokeResult" runat="server" ForeColor="Red" Width="229px"></asp:Label></td> </tr> </table>

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The flow for the code behind page is as follows.

Imports System.Web.Security Imports System.Web.UI Imports System.Web.UI.WebControls Imports System.Web.UI.WebControls.WebParts Imports System.Web.UI.HtmlControls Imports System.Reflection Class _Default Inherits System.Web.UI.Page ' Private type As Type = Nothing Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load type = GetType(InstanceClass) End Sub Protected Function getObjectProperty(ByVal str As String) As String Dim retValue As String = "" Try Dim o As Object = Activator.CreateInstance(type, New Object() {Me.txtPropertyValue.Text.Trim()}) Dim pi As PropertyInfo = type.GetProperty("ReturnValue", GetType(String)) retValue = pi.GetValue(o, Nothing).ToString() Catch ex As Exception Console.WriteLine(ex.Message) End Try Return retValue End Function Protected Function getOjbectMethod(ByVal str As String) As String Dim retValue As Object = Nothing Try Dim o As Object = Activator.CreateInstance(type) Dim mi As MethodInfo = type.GetMethod("getFunction", BindingFlags.Public Or BindingFlags.Instance, Nothing, New Type() {GetType(String)}, Nothing) retValue = mi.Invoke(o, New Object() {str}) Catch ex As Exception Console.WriteLine(ex.Message) End Try Return retValue.ToString() End Function Protected Sub btnGetProperty_Click(ByVal sender As Object, ByVal e As EventArgs) Me.lblPropertyResult.Text = Me.getObjectProperty(Me.txtPropertyValue.Text.Trim()) End Sub Protected Sub btnInvoke_Click(ByVal sender As Object, ByVal e As EventArgs) Me.lblInvokeResult.Text = Me.getOjbectMethod(Me.txtParameter.Text.Trim()) End Sub End Class

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