vb.net 在运行时动态创建类
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Create Class dynamically at runtime
提问by Vahid Farahmandian
I have a method like this: (this is a generic method, and DYNAMIC_CLASS_TYPEwill be changed in situation to other situation)
我有一个这样的方法：（这是一个通用方法，DYNAMIC_CLASS_TYPE会根据情况更改为其他情况）
Dim res = f.MyMethod(Of DYNAMIC_CLASS_TYPE)("select Id, Name from myTable")
I want to create a dynamic class, based on my query's columns and then pass the class instead of DYNAMIC_CLASS_TYPE.
我想根据查询的列创建一个动态类，然后传递类而不是DYNAMIC_CLASS_TYPE.
How can I do this?
我怎样才能做到这一点？
采纳答案by Vahid Farahmandian
I finally succeeded in doing it. My Code is as:
我终于成功了。我的代码是：
Public Shared Function CreateClass(ByVal className As String, ByVal properties As Dictionary(Of String, Type)) As Type
Dim myDomain As AppDomain = AppDomain.CurrentDomain
Dim myAsmName As New AssemblyName("MyAssembly")
Dim myAssembly As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, AssemblyBuilderAccess.Run)
Dim myModule As ModuleBuilder = myAssembly.DefineDynamicModule("MyModule")
Dim myType As TypeBuilder = myModule.DefineType(className, TypeAttributes.Public)
myType.DefineDefaultConstructor(MethodAttributes.Public)
For Each o In properties
Dim prop As PropertyBuilder = myType.DefineProperty(o.Key, PropertyAttributes.HasDefault, o.Value, Nothing)
Dim field As FieldBuilder = myType.DefineField("_" + o.Key, o.Value, FieldAttributes.[Private])
Dim getter As MethodBuilder = myType.DefineMethod("get_" + o.Key, MethodAttributes.[Public] Or MethodAttributes.SpecialName Or MethodAttributes.HideBySig, o.Value, Type.EmptyTypes)
Dim getterIL As ILGenerator = getter.GetILGenerator()
getterIL.Emit(OpCodes.Ldarg_0)
getterIL.Emit(OpCodes.Ldfld, field)
getterIL.Emit(OpCodes.Ret)
Dim setter As MethodBuilder = myType.DefineMethod("set_" + o.Key, MethodAttributes.[Public] Or MethodAttributes.SpecialName Or MethodAttributes.HideBySig, Nothing, New Type() {o.Value})
Dim setterIL As ILGenerator = setter.GetILGenerator()
setterIL.Emit(OpCodes.Ldarg_0)
setterIL.Emit(OpCodes.Ldarg_1)
setterIL.Emit(OpCodes.Stfld, field)
setterIL.Emit(OpCodes.Ret)
prop.SetGetMethod(getter)
prop.SetSetMethod(setter)
Next
Return myType.CreateType()
End Function
The return value of the function is a Type of my Custom Class.
函数的返回值是我的自定义类的类型。
回答by Jacek_D73
There seems to be a bug. I think this line:
似乎有一个错误。我认为这一行：
Dim field As FieldBuilder = myType.DefineField("_" + o.Key, GetType(Integer), FieldAttributes.[Private])
should look like this:
应该是这样的：
Dim field As FieldBuilder = myType.DefineField("_" + o.Key, o.Value, FieldAttributes.[Private])
Regards.
问候。
回答by Lunadix
This line:
这一行：
Dim field As FieldBuilder = myType.DefineField("_" + o.Key, GetType(Integer), FieldAttributes.[Private])
must to be replaced with this:
必须用这个替换：
Dim field As FieldBuilder = myType.DefineField("_" + o.Key, o.Value, FieldAttributes.[Private])
回答by Steve
A much simpler way is to use the System.Activator:
更简单的方法是使用 System.Activator：
Activator.CreateInstance(YourType, ParramArrayOfYourVariablesForNEW)
So say I have a class (Test) that takes a single string in the initialization
所以说我有一个类 (Test) 在初始化中采用单个字符串
Public Class Test
Public Sub New(byval MyString as string)
...
You could create a new instance like this:
您可以像这样创建一个新实例：
Activator.CreateInstance(gettype(Test),"My String")
