C#Emit，如何编写if语句 [英] C# Emit , how to write a if statement
问题描述
首先，我有一堂课
internal class Parent
{
protected void Write(string message, [CallerMemberName] string caller = null)
{
Console.WriteLine($"{caller} :: {message}");
}
}
并且我想动态创建一个类，该类具有属性名称"，如果属性值更改，则调用write方法，看起来像
and i want to dynamic create a class , the class has a property "Name", if the property value changed then call write method , looks like
class Child : Parent
{
private string _name;
public string Name
{
get { return _name; }
set
{
if (_name != value)
{
Write("changedto: " + value);
_name = value;
}
}
}
}
我想知道的是高亮子句. 如何将其写入. 请帮忙.
what i want to know is the highlight clause. how to write it in emit. please help.
我想要下面的代码
private static MethodBuilder BuildSetter(TypeBuilder typeBuilder, PropertyInfo property, FieldBuilder fieldBuilder, MethodAttributes attributes)
{
var setterBuilder = typeBuilder.DefineMethod($"set_{property.Name}", attributes, null, new Type[] { property.PropertyType });
var ilGenerator = setterBuilder.GetILGenerator();
ilGenerator.Emit(OpCodes.Ldarg_0); //this
ilGenerator.Emit(OpCodes.Ldarg_1); // the first one in arguments list
//code should be here
ilGenerator.Emit(OpCodes.Stfld, fieldBuilder);
ilGenerator.Emit(OpCodes.Ret);
return setterBuilder;
}
已更新
var typeBuilder = moduleBuilder.DefineType(typeName, TypeAttributes.Public,typeof(PropertyChanged));
var t = typeof(PropertyChanged);
var m2 = t.GetMethod("ValueChanged");
您看到的是，当我创建类型时，我使用的是父类型，而在父类型中，有一个名为"ValueChanged"的方法
you see , when i create the type , i use a Parent type , and in the parent type there is a method called "ValueChanged"
protected void ValueChanged(object value,[CallerMemberName] string property = null)
我想在set方法中调用它.
i want call it in set method.
更新2
private static MethodBuilder BuildSetter(TypeBuilder typeBuilder, PropertyInfo property, FieldBuilder fieldBuilder, MethodAttributes attributes)
{
var propertyType = property.PropertyType;
var setterBuilder = typeBuilder.DefineMethod($"set_{property.Name}", attributes, null, new Type[] { propertyType });
var setIl = setterBuilder.GetILGenerator();
Label exitSet = setIl.DefineLabel(); // define label to jump in case condition is false
setIl.Emit(OpCodes.Ldarg_0); // this
setIl.Emit(OpCodes.Ldfld, fieldBuilder); // _name field
setIl.Emit(OpCodes.Ldarg_1); // value
var inequality = propertyType.GetMethod("Equals", new[] { propertyType});
setIl.Emit(OpCodes.Callvirt, inequality); // '!=' method
setIl.Emit(OpCodes.Brtrue_S, exitSet); // check for inequality
setIl.Emit(OpCodes.Ldarg_0); // load string literal
setIl.Emit(OpCodes.Ldarg_1); // value
setIl.Emit(OpCodes.Ldstr, property.Name);
var m = typeBuilder.BaseType.GetMethod("ValueChanged", new Type[] {typeof(object),typeof(string) });
setIl.Emit(OpCodes.Call, m);
setIl.Emit(OpCodes.Ldarg_0); // this
setIl.Emit(OpCodes.Ldarg_1); // value
setIl.Emit(OpCodes.Stfld, fieldBuilder); // save the new value into _name
setIl.MarkLabel(exitSet); // mark the label
setIl.Emit(OpCodes.Ret); // return
return setterBuilder;
}
更新3 屏幕快照
update 3 screen-snaps
更新4
也许，我已经找到错误原因，请参见反射发射和类型继承:调用基类型构造函数
maybe , i have found the error reason , see Reflection Emit and Type Inheritance: Calling Base Type Constructors
更新5
最后，我得到了错误原因.这不是我在更新4上猜到的，它是由调用parent't方法"ValueChanged"引起的.如果原始数据类型为 IsValueType ，则在将参数传输到方法之前，应将其作为对象装箱.参见下面的参考资料，
finally , i got the error reason . it was not what i guessed at update 4 , it was caused by calling parent't method "ValueChanged" . before we transfer the parameter to the method , we should Box it as Object if the original data type is IsValueType . see the reference below ,
推荐答案
@AlbertK答案向您展示了正确的方法，我将添加完整的代码.希望对您有所帮助.
@AlbertK answer shows you the right way, I'll add the complete code. Hope it will help.
我将所有内容都放在一种方法中.按照您的意愿进行重构.
I put everything in one method.. refactor it as you wish.
// define assembly and module
var propertyName = "Name";
var propertyType = typeof(string);
var ab = AssemblyBuilder.DefineDynamicAssembly(
new AssemblyName("dynamicAssembly"),
AssemblyBuilderAccess.Save);
var mb = ab.DefineDynamicModule("dynamicModule", "dynamicModule.dll");
// define type, field and property
var tb = mb.DefineType("dynamicType");
var fb = tb.DefineField("_name", propertyType, FieldAttributes.Private);
var pb = tb.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, Type.EmptyTypes);
var get = tb.DefineMethod("get_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, propertyType, Type.EmptyTypes);
var set = tb.DefineMethod("set_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, null, new[] { propertyType });
// write the IL for the get method
var getIl = get.GetILGenerator();
getIl.Emit(OpCodes.Ldarg_0); // this
getIl.Emit(OpCodes.Ldfld, fb); // _name field
getIl.Emit(OpCodes.Ret);
// write the IL for the set method
var setIl = set.GetILGenerator();
Label exitSet = setIl.DefineLabel(); // define label to jump in case condition is false
setIl.Emit(OpCodes.Ldarg_0); // this
setIl.Emit(OpCodes.Ldfld, fb); // _name field
setIl.Emit(OpCodes.Ldarg_1); // value
var inequality = propertyType.GetMethod("op_Inequality", new[] { propertyType, propertyType });
setIl.Emit(OpCodes.Call, inequality); // '!=' method
setIl.Emit(OpCodes.Brfalse_S, exitSet); // check for inequality
setIl.Emit(OpCodes.Ldstr, "changedto:"); // load string literal
setIl.Emit(OpCodes.Ldarg_1); // value
var concat = propertyType.GetMethod("Concat", new[] { propertyType, propertyType });
setIl.Emit(OpCodes.Call, concat); // concat two strings (literal + value)
var writeline = typeof(Console).GetMethod("WriteLine", new[] { propertyType });
setIl.Emit(OpCodes.Call, writeline); // write
setIl.Emit(OpCodes.Ldarg_0); // this
setIl.Emit(OpCodes.Ldarg_1); // value
setIl.Emit(OpCodes.Stfld, fb); // save the new value into _name
setIl.MarkLabel(exitSet); // mark the label
setIl.Emit(OpCodes.Ret); // return
pb.SetGetMethod(get);
pb.SetSetMethod(set);
tb.CreateType(); // complete the type
ab.Save("dynamicModule.dll"); // save the assembly to disk
结果
internal class dynamicType
{
private string _name;
public string Name
{
get
{
return this._name;
}
set
{
if (this._name != value)
{
Console.WriteLine("changedto:" + value);
this._name = value;
}
}
}
}
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