我有一个类,它看起来像这样:
public class Field
{
public string FieldName;
public string FieldType;
}
和一个对象列表<字段>值:
{"EmployeeID","int"},
{"EmployeeName","String"},
{"Designation","String"}
我想创建一个类,看起来像这样:
Class DynamicClass
{
int EmployeeID,
String EmployeeName,
String Designation
}
有什么办法可以做到吗?
我希望它在运行时生成。我不希望在文件系统中驻留一个物理CS文件。
您还可以使用DynamicObject动态创建类。
public class DynamicClass : DynamicObject
{
private Dictionary<string, KeyValuePair<Type, object>> _fields;
public DynamicClass(List<Field> fields)
{
_fields = new Dictionary<string, KeyValuePair<Type, object>>();
fields.ForEach(x => _fields.Add(x.FieldName,
new KeyValuePair<Type, object>(x.FieldType, null)));
}
public override bool TrySetMember(SetMemberBinder binder, object value)
{
if (_fields.ContainsKey(binder.Name))
{
var type = _fields[binder.Name].Key;
if (value.GetType() == type)
{
_fields[binder.Name] = new KeyValuePair<Type, object>(type, value);
return true;
}
else throw new Exception("Value " + value + " is not of type " + type.Name);
}
return false;
}
public override bool TryGetMember(GetMemberBinder binder, out object result)
{
result = _fields[binder.Name].Value;
return true;
}
}
我将所有类字段连同它们的类型和值一起存储在字典_fields中。这两种方法都可以获取或设置一些属性的值。必须使用dynamic关键字创建该类的实例。
使用你的例子:
var fields = new List<Field>() {
new Field("EmployeeID", typeof(int)),
new Field("EmployeeName", typeof(string)),
new Field("Designation", typeof(string))
};
dynamic obj = new DynamicClass(fields);
//set
obj.EmployeeID = 123456;
obj.EmployeeName = "John";
obj.Designation = "Tech Lead";
obj.Age = 25; //Exception: DynamicClass does not contain a definition for 'Age'
obj.EmployeeName = 666; //Exception: Value 666 is not of type String
//get
Console.WriteLine(obj.EmployeeID); //123456
Console.WriteLine(obj.EmployeeName); //John
Console.WriteLine(obj.Designation); //Tech Lead
编辑:下面是我的类Field的外观:
public class Field
{
public Field(string name, Type type)
{
this.FieldName = name;
this.FieldType = type;
}
public string FieldName;
public Type FieldType;
}
根据@danijels的回答,在VB中动态创建一个类。NET:
Imports System.Reflection
Imports System.Reflection.Emit
Public Class ObjectBuilder
Public Property myType As Object
Public Property myObject As Object
Public Sub New(fields As List(Of Field))
myType = CompileResultType(fields)
myObject = Activator.CreateInstance(myType)
End Sub
Public Shared Function CompileResultType(fields As List(Of Field)) As Type
Dim tb As TypeBuilder = GetTypeBuilder()
Dim constructor As ConstructorBuilder = tb.DefineDefaultConstructor(MethodAttributes.[Public] Or MethodAttributes.SpecialName Or MethodAttributes.RTSpecialName)
For Each field In fields
CreateProperty(tb, field.Name, field.Type)
Next
Dim objectType As Type = tb.CreateType()
Return objectType
End Function
Private Shared Function GetTypeBuilder() As TypeBuilder
Dim typeSignature = "MyDynamicType"
Dim an = New AssemblyName(typeSignature)
Dim assemblyBuilder As AssemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(an, AssemblyBuilderAccess.Run)
Dim moduleBuilder As ModuleBuilder = assemblyBuilder.DefineDynamicModule("MainModule")
Dim tb As TypeBuilder = moduleBuilder.DefineType(typeSignature, TypeAttributes.[Public] Or TypeAttributes.[Class] Or TypeAttributes.AutoClass Or TypeAttributes.AnsiClass Or TypeAttributes.BeforeFieldInit Or TypeAttributes.AutoLayout, Nothing)
Return tb
End Function
Private Shared Sub CreateProperty(tb As TypeBuilder, propertyName As String, propertyType As Type)
Dim fieldBuilder As FieldBuilder = tb.DefineField("_" & propertyName, propertyType, FieldAttributes.[Private])
Dim propertyBuilder As PropertyBuilder = tb.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, Nothing)
Dim getPropMthdBldr As MethodBuilder = tb.DefineMethod("get_" & propertyName, MethodAttributes.[Public] Or MethodAttributes.SpecialName Or MethodAttributes.HideBySig, propertyType, Type.EmptyTypes)
Dim getIl As ILGenerator = getPropMthdBldr.GetILGenerator()
getIl.Emit(OpCodes.Ldarg_0)
getIl.Emit(OpCodes.Ldfld, fieldBuilder)
getIl.Emit(OpCodes.Ret)
Dim setPropMthdBldr As MethodBuilder = tb.DefineMethod("set_" & propertyName, MethodAttributes.[Public] Or MethodAttributes.SpecialName Or MethodAttributes.HideBySig, Nothing, {propertyType})
Dim setIl As ILGenerator = setPropMthdBldr.GetILGenerator()
Dim modifyProperty As Label = setIl.DefineLabel()
Dim exitSet As Label = setIl.DefineLabel()
setIl.MarkLabel(modifyProperty)
setIl.Emit(OpCodes.Ldarg_0)
setIl.Emit(OpCodes.Ldarg_1)
setIl.Emit(OpCodes.Stfld, fieldBuilder)
setIl.Emit(OpCodes.Nop)
setIl.MarkLabel(exitSet)
setIl.Emit(OpCodes.Ret)
propertyBuilder.SetGetMethod(getPropMthdBldr)
propertyBuilder.SetSetMethod(setPropMthdBldr)
End Sub
End Class