错误 CS0266 无法将类型 'System.Linq.IQueryable<string>' 隐式转换为 'ExerciseDAL.Department'

Question

当我在网站界面上输入员工姓氏时，我试图显示部门名称，这就是我遇到问题的地方！命名空间 ExerciseDAL { public class 部门DAO {

    public DepartmentDAO() { }

    public Department GetById(string departId)
    {

        Department reDpt = null;
        DbContext _ctx;

        try
        {
            _ctx = new DbContext();
            var departments = _ctx.Departments;
            var dept = departments.AsQueryable<Department>().FirstOrDefault(dpt => dpt.Id.ToString() == departId);
            reDpt = dept;
        }
        catch (Exception ex)
        {
            Console.WriteLine("Problem " + ex.Message);
        }
        return reDpt;
    }
}
}

如您所见，出发是我收到错误 CS0266 的地方。 dept.id 是一个对象，我必须将它与字符串进行比较，但是当我这样做时它无法编译。

部门Class：

 namespace ExerciseDAL
{
public class Department
 {
    public ObjectId Id { get; set; } //represents primary key
    public string DepartmentName { get; set; }
}
}

DepartmentViewModel：我也将更改此处的代码，因为我知道这是错误的。

命名空间 ExerciseViewModel { public class DepartmentViewModel { 私人部门DAO _daos;

    public string DepartmentsId { get; set; } //represents primary key
    public string DepartmentName { get; set; }

    public DepartmentViewModel()
    {
        _daos = new DepartmentDAO();
    }



    public void GetByDepart()
    {
        try
        {
            Department dpt = _daos.GetById(DepartmentsId);
            DepartmentsId = dpt.Id.ToString();
            DepartmentName = DepartmentName;
        }
        catch (Exception ex)
        {
            DepartmentsId = "not Found!";
        }
    }
}
}

DepartmentController：我也将更改此处的代码，因为我知道这是错误的。

命名空间 ExerciseWebSite { public class 部门控制器：ApiController {

    [Route("api/department/{departmentId}")]
    public IHttpActionResult Get(string departmentId)
    {
        try
        {
            DepartmentViewModel dpt = new DepartmentViewModel();
            dpt.DepartmentsId = departmentId;
            dpt.GetByDepart();
            return Ok(dpt);
        }
        catch (Exception ex)
        {
            return BadRequest("retrieve faild - " + ex.Message);
        }
    }

}
}

Employee.js:

 $(function () {
$("#empbutton").click(function (e) {
    var last = $("#TextBoxLastname").val();
    ajaxCall("Get", "api/employees/" + last, "").done(function (data) {
        if (data.Lastname !== "not found") {
            $("#email").text(data.Email);
            $("#title").text(data.Title);
            $("#firstname").text(data.Firstname);
            $("#phone").text(data.Phoneno);

            ajaxCall("Get", "api/department/" + data.Id)
            .done(function (depdata)
            {
                $("#departmentname").text(depdata.DepartmentName);
            })
            .fail(function (jqXHR, textStatus, errorThrown)
            { errorRoutine(jqXHR); });
        }//end of if
        else {
            $("#firstname").text("Not Found");
            $("#email").text("");
            $("#title").text("");
            $("#phone").text("");
            $("#departmentname").text("");
        }//end of else
    }).fail(function (jqXHR, textStatus, errorThrown)
    { errorRoutine(jqXHR); });//end of ajax

Answer 1

你的"from...where..."表达returns几个部门，但你只需要一个。

试试这个：

var dept = departments.Where(x=>x.Id == departId).Single();

或者将您的 reDpt 对象类型从 Department 更改为允许多个值的类型，例如 List。

错误 CS0266 无法将类型 'System.Linq.IQueryable<string>' 隐式转换为 'ExerciseDAL.Department'

Error CS0266 Cannot implicitly convert type 'System.Linq.IQueryable<string>' to 'ExerciseDAL.Department'

javascript

java

jquery

client-server