我尝试动态地为Linq查询创建一个表达式,但它只返回此消息:
{{方法=内部错误评估表达式}我使用Vs 2019和.NET Core 3.1。客户类别{公共字符串名称{get;组; }...}
var parameter = Expression.Parameter(typeof(Client), "x");
var member = Expression.Property(parameter, "Name");
var constant = Expression.Constant("X Y");
var exp = Expression.Equal(member, constant);
var func = Expression.Lambda(exp, parameter).Compile();
请问我在哪里出错?
更新
namespace Domain
{
public class Client
{
public string Name { get; set; }
public string UserName { get; set; }
public string Department { get; set; }
public string CompanyPhoneNumber { get; set; }
public string PrivateMobileNumber { get; set; }
public string ComputerName { get; set; }
public Guid InternetProviderId { get; set; }
public virtual InternetProvider InternetProvider { get; set; }
public string OtherInternetProvider { get; set; }
}
}
Expression.Lambda
方法具有允许指定委托类型的通用版本,最后一行可以修改为:
var func = Expression.Lambda<Func<Client, bool>>(exp, parameter).Compile();
使用示例:
var list = new List<Client>
{
new Client() { Name = "X Y"}
};
var l2 = list.Where(func).ToList();
工作示例:here。