c#从字符串表示Lambda到Func <T>

Question

我尝试从string实现e动态Funx表达式

Expression<Func<CustomerDto, object>> expr = (src) => src.Customer.Id;
Func<CustomerDto, object> delg = expr.Compile();
var id = delg.Invoke(customerListDtos[0]);

并返回id(es.123)

所以现在我尝试从string创建表达式

    public Expression<Func<T, object>> GetLambda<T>(string property)
    {

        var param = Expression.Parameter(typeof(T), "p");
        Expression body = param;
        foreach (var member in property.Split('.'))
        {
            body = Expression.PropertyOrField(body, member);
        }
        //return Expression.Lambda(body, param);

        //Expression parent = Expression.Property(param, property);
        Expression parent = Expression.Lambda(body, param);
        //if (!parent.Type.IsValueType)
        //{
        //    return Expression.Lambda<Func<T, object>>(parent, param);
        //}
        var convert = Expression.Convert(parent, typeof(object));
        return Expression.Lambda<Func<T, object>>(convert, param);
    }

因此,如果我从GetLambda调用结果,则输出不是123,而是

 var data = GetLambda<CustomerDto>("Customer.Id");
 Func<CustomerDto, object> g = data.Compile();
 var id = g(customerListDtos[0]);

结果是

{Method = {Int64 lambda_method(System.Runtime.CompilerServices.Closure, ef.Customer.CustomerDto)}}

Answer 1

你打电话Expression.Labmda两次,基本上把一个func包装成另一个.试试这个:

public static Expression<Func<T, object>> GetLambda<T>(string property) {
    var param = Expression.Parameter(typeof(T), "p");
    Expression body = param;
    foreach (var member in property.Split('.')) {
        body = Expression.PropertyOrField(body, member);
    }
    var convert = Expression.Convert(body, typeof(object));
    return (Expression<Func<T, object>>) Expression.Lambda(convert, param);
}