本质上,我正在尝试使用表达式树来执行此操作
var properties = new Dictionary<string, object>();
foreach (var propInfo in objType.GetTypeInfo().GetProperties(BindingFlags.Public))
{
var name = propInfo.Name;
var value = propInfo.GetValue(objInstance);
properties.Add(name, value);
}
return properties;
IE。创建名称和值对的字典,其中name是
objType
的属性的名称,value是objInstance
的实例objType
的属性的值现在将其转换为表达式应编译为一个简单的委托(delegate)
Func<T, Dictionary<string, object>> func = i =>
{
var properties = new Dictionary<string, object>();
properties.Add("Prop1", (object)i.Prop1);
properties.Add("Prop2", (object)i.Prop2);
properties.Add("Prop3", (object)i.Prop3);
// depending upon the number of properties of T, Add will continue
return properties;
};
我知道如何执行其中的一些操作,但是我不确定如何创建字典的本地实例,然后在后续表达式中使用它(并将其返回)?
最佳答案
它应该类似于(内联注释):
public static Func<T, Dictionary<string, object>> GetValuesFunc<T>()
{
Type objType = typeof(T);
var dict = Expression.Variable(typeof(Dictionary<string, object>));
var par = Expression.Parameter(typeof(T), "obj");
var add = typeof(Dictionary<string, object>).GetMethod("Add", BindingFlags.Public | BindingFlags.Instance, null, new[] { typeof(string), typeof(object) }, null);
var body = new List<Expression>();
body.Add(Expression.Assign(dict, Expression.New(typeof(Dictionary<string, object>))));
var properties = objType.GetTypeInfo().GetProperties(BindingFlags.Public | BindingFlags.Instance);
for (int i = 0; i < properties.Length; i++)
{
// Skip write only or indexers
if (!properties[i].CanRead || properties[i].GetIndexParameters().Length != 0)
{
continue;
}
var key = Expression.Constant(properties[i].Name);
var value = Expression.Property(par, properties[i]);
// Boxing must be done manually... For reference type it isn't a problem casting to object
var valueAsObject = Expression.Convert(value, typeof(object));
body.Add(Expression.Call(dict, add, key, valueAsObject));
}
// Return value
body.Add(dict);
var block = Expression.Block(new[] { dict }, body);
var lambda = Expression.Lambda<Func<T, Dictionary<string, object>>>(block, par);
return lambda.Compile();
}
像这样使用它:
public class Test
{
public int A { get; set; }
public string B { get; set; }
}
和
Func<Test, Dictionary<string, object>> fn = GetValuesFunc<Test>();
var obj = new Test
{
A = 5,
B = "Foo"
};
var res = fn(obj);
关于c# - 表达式树创建具有类属性值的字典,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/43277722/