Classic Tutorial: Creating an instance of a class with. Net

Read a lot of online about dotnet dynamic Create class instances of the article, I want to sum up here, in fact, the method is very simple, is to use "Activator.CreateInstance". However, this method requires the type of the class to be created as an argument, and in order to obtain that parameter, [Assembly] can be used. GetType method, this method requires only the name (name string) of the class to be created, and the final question is to obtain the assembly in which the class resides. This solves the problem of how to get the assembly that contains the class that you want to create.

You can refer to the http://www.cnblogs.com/ShadowK/archive/2006/11/14/560131.html, a lot of text wrote a relatively complete dynamic construction of the Class Designer. In fact, there can be an easier way to get the assembly, and here's what I do.

Using Microsoft.VisualBasic.VBCodeProvider (), if C # can be CSharpCodeProvider (), compile the class file into a DLL file, and then use [Assembly]. LoadFrom ("The absolute path of the DLL") loads the DLL. This allows us to avoid complex code that creates DLLs and type. I told my project team members This example, after emphasizing to open the mind, simple is perfect, always try to find an easy way to achieve, customers will never for our complex code to spend a penny more.

1. How to perform a compilation task:

The following are the referenced contents: The public Shared function compileexecutable () function compileexecutable (ByVal sourceName As String, ByVal DllPath as String, ByRef Returndllname as String) as Boolean Dim sourcefile as FileInfo = New FileInfo (sourceName) Dim provider as CodeDomProvider = Nothing Dim Compileok as Boolean = False ' Select Code provider based on the extension of the original file If sourceFile.Extension.ToUpper (CultureInfo.InvariantCulture) = ". CS" Then Provider = New Microsoft.CSharp.CSharpCodeProvider () ElseIf sourceFile.Extension.ToUpper (CultureInfo.InvariantCulture) = ". VB "Then Provider = New Microsoft.VisualBasic.VBCodeProvider () Else Console.WriteLine ("Original file must contain. cs or. vb extension") End If If not provider are nothing Then ' Construct the full path of the DLL file Dim dllName as String = String.Format ("{0}\{1}.dll", _ DllPath, _ SourceFile.Name.Replace (".", "_")) Returndllname = DllName Dim cp as CompilerParameters = New CompilerParameters () ' Set compilation control parameters Cp. GenerateExecutable = False to generate DLL, if true to generate EXE file Cp. outputassembly = DllName Cp. GenerateInMemory = False Cp. TreatWarningsAsErrors = False ' Invoke the compilation method to compile the original code file into a DLL Dim cr as CompilerResults = Provider.compileassemblyfromfile (cp, _ SourceName) If Cr. Errors.Count > 0 Then ' Show compilation errors Console.WriteLine (Compile error {0} compiled to {1}), _ SourceName, Cr. pathtoassembly) Dim CE as CompilerError For all CE in CR. Errors Console.WriteLine ("{0}", CE. ToString ()) Console.WriteLine () Next CE Else ' Shows the success of the compilation message Console.WriteLine ("Original file {0} compiled into {1} completed successfully.", _ SourceName, Cr. pathtoassembly) End If ' Returns the result of the compilation If Cr. Errors.Count > 0 Then Compileok = False Else Compileok = True End If End If Return Compileok End Function

2. Compile the DLL and dynamically create instances of the class. (The original file for this class is the Class1.vb file, placed in the App_Code folder of website, and can be placed in any physical location when used in practice.) )

The following are the referenced contents: Dim strsourcefilename as String = Server.MapPath ("~/app_code/class1.vb") ' Full path to ' class file Dim Strdllpath as String = Server.MapPath ("~/app_code") ' where the compiled DLL file is stored Dim strdllname as String = "" "DLL's full path (return value) Compileexecutable (Strsourcefilename, Strdllpath, Strdllname) ' compiles the original file as a DLL file Dim A As [Assembly] = [Assembly]. LoadFrom (strdllname) ' Load DLL Dim MyType as System.Type = A.gettype ("Class1") ' Gets the Type of the Class1 Dim obj as Object = activator.createinstance (MyType) ' obtains an instance of Class1

3.class1.vb Original Document

The following are the referenced contents: Public Class Class1class Class1 Public I as Integer End Class