Question

我在下面的代码中得到一个错误，它说我无法将方法组ListStudents转换为generic.list，如果我在ListStudents的末尾尝试（）我得到：cant将数组转换为列表

所有即时尝试都是将一些用户硬编码到一个数组并在我的GET请求中返回它是否有解决方法？

    [WebInvoke(Method = "GET", BodyStyle = WebMessageBodyStyle.Bare, RequestFormat = WebMessageFormat.Xml, ResponseFormat = WebMessageFormat.Xml, UriTemplate = "")]
    List<Student> GetStudentCollection();
}
[DataContract(Name="Student")]
public class Student
{
    [DataMember(Name = "StudentID")]
    public string StudentID { get; set; }
    [DataMember(Name = "FirstName")]
    public string FirstName { get; set; }
    [DataMember(Name = "LastName")]
    public string LastName { get; set; }

}
public class RawDataService : IReceiveData
{
    public Student[] ListStudents()
    {
       List<Student> student = new List<Student>()
       {
           new Student { StudentID="bla", FirstName="bla", LastName="bla"},
           new Student { StudentID="bla1", FirstName="bla1", LastName="bla1"},
           new Student { StudentID="bla2", FirstName="bla2", LastName="bla2"}
       };
        return student.ToArray();
    }

    public List<Student> GetStudentCollection()
    {
        return ListStudents(); //error on this line, cant convert array to list
    }

Answer 1

ListStudents是一种方法，而不是属性，所以试试这个：

return ListStudents();

另外，更改ListStudents()方法以返回List，如下所示：

    public List<Student> ListStudents()
    {
        List<Student> student = new List<Student>()
        {
            new Student { StudentID="bla", FirstName="bla", LastName="bla"},
            new Student { StudentID="bla1", FirstName="bla1", LastName="bla1"},
            new Student { StudentID="bla2", FirstName="bla2", LastName="bla2"}
        };
        return student;
    }

Answer 2

尝试使用ToList linq扩展方法：

using System.Linq;

...

public Student[] ListStudents()
{
   List<Student> student = new List<Student>()
   {
       new Student { StudentID="bla", FirstName="bla", LastName="bla"},
       new Student { StudentID="bla1", FirstName="bla1", LastName="bla1"},
       new Student { StudentID="bla2", FirstName="bla2", LastName="bla2"}
   };
    return student.ToArray();
}

public List<Student> GetStudentCollection()
{
    return ListStudents().ToList(); //<-- this is the change you need
}

但是，要减少转化次数，我建议您更改方法如下：

public Student[] ListStudents()
{
   return GetStudentCollection().ToArray();
}

public IList<Student> GetStudentCollection()
{
   var students = new List<Student>()
   {
       new Student { StudentID="bla", FirstName="bla", LastName="bla"},
       new Student { StudentID="bla1", FirstName="bla1", LastName="bla1"},
       new Student { StudentID="bla2", FirstName="bla2", LastName="bla2"}
   };

   return students();
}

Answer 3

除非您有使用数组的原因，否则只返回列表。为什么要花费CPU转换为数组，然后备份到List：

public class RawDataService : IReceiveData
{
    public List<Student> ListStudents()
    {
       List<Student> students = new List<Student>()
       {
           new Student { StudentID="bla", FirstName="bla", LastName="bla"},
           new Student { StudentID="bla1", FirstName="bla1", LastName="bla1"},
           new Student { StudentID="bla2", FirstName="bla2", LastName="bla2"}
       };
        return students;
    }

    public List<Student> GetStudentCollection()
    {
        return ListStudents(); //error on this line, cant convert array to list
    }

但是，如果必须返回数组，则将错误的行更改为：

  using System.Linq;
  ...
  return ListStudents().ToList();

无法转换方法组或将数组转换为列表作为其方法

3 个答案: