Question

我正在寻找一种从包含Linq表达式本身的字符串创建表达式的方法。

假设以下课程：

public class Person
{
    public string Name { get; set; }

    public string FirstName { get; set; }

    public Address[] Address { get; set; }
}

public class Address
{
    public string City { get; set; }
}

可以使用以下代码生成简单表达式：

var expression = @"x.Name";
var p = Expression.Parameter(typeof(Person), "x");
var e = System.Linq.Dynamic.DynamicExpression.ParseLambda(new[] { p }, null, expression);

以下示例将按预期返回Name 1：

static void Main(string[] args)
{
    var personsCollection = new List<Person>
    {
        new Person { Name = "Name 1", FirstName = "Firstname 1", Address = new Address { City = "City 1" } },
        new Person { Name = "Name 2", FirstName = "Firstname 2", Address = new Address { City = "City 2" } }
    };

    var expression = @"x.Name";
    var p = Expression.Parameter(typeof(Person), "x");
    var e = System.Linq.Dynamic.DynamicExpression.ParseLambda(new[] { p }, null, expression);

    var result = e.Compile().DynamicInvoke(personsCollection[0]);
}

现在，假设我将表达式更改为投射List<T>。表达式将是：var expression = @"x.Address.Select(dest => new { MyCity = dest.City })";

使用以上示例代码会抛出以下异常："Unknown identifier 'dest'"

关于如何解决这个问题的任何想法？

从包含LINQ表达式的字符串创建表达式

0 个答案: