动态创建表达式树
本文关键字:表达式 创建 动态 | 更新日期: 2023-09-27 18:04:36
我有一个想法,想知道它是否可以工作。我有一个简单的类与属性,并希望与表达式生成访问器。但最后我需要一个Func<Test, string>
,但我不知道使用它们的类型。一个小例子
class Program
{
static void Main(string[] args)
{
Test test = new Test();
test.TestString = "Blubb";
var actionStub = typeof(Helper).GetMethod("CreatePropertyGetter").MakeGenericMethod(new Type[] { test.GetType(), typeof(string)});
dynamic action = actionStub.Invoke(null, new object[] {test.GetType(), "TestString"});
var x = action(test);
}
}
public class Test
{
public string TestString { get; set; }
}
public static class Helper
{
public static Func<TType, TPropValueType> CreatePropertyGetter<TType, TPropValueType>(Type type,
string propertyName)
{
PropertyInfo fieldInfo = type.GetProperty(propertyName);
ParameterExpression targetExp = Expression.Parameter(typeof(TType), "target");
MemberExpression fieldExp = Expression.Property(targetExp, fieldInfo);
UnaryExpression assignExp = Expression.Convert(fieldExp, typeof(TPropValueType));
Func<TType, TPropValueType> getter =
Expression.Lambda<Func<TType, TPropValueType>>(assignExp, targetExp).Compile();
return getter;
}
}
问题是我不能调用表达式没有动态,因为我不能简单地将其转换为Func<object, object>
您正在生成(TType target) => target.Something
。相反,生成(object target) => (object)((TType)target).Something
以便您可以使用Func<object, object>
。
不清楚你到底在要求什么,但这里有一个例子,你可以使它Func<object, object>
:
public static class Helper
{
public static Func<object, object> CreatePropertyGetter(Type type, string propertyName)
{
var fieldInfo = type.GetProperty(propertyName);
var targetExp = Expression.Parameter(typeof(object), "target");
var fieldExp = Expression.Property(Expression.ConvertChecked(targetExp, type), fieldInfo);
var getter = Expression.Lambda<Func<object, object>>(fieldExp,targetExp).Compile();
return getter;
}
}