LINQ查询以从另一个表获取数据

Question

I have two tables

I am trying to write a LINQ Query where I want to select everything in Table 1 but instead of CaseStatusID, I want to return the actual status (Corresponding to CaseStatusID in Table 2).

I have the query but I the error Cannot convert expression type 'System.Collections.Generic.List<CaseId:int, Status:string>' to return type 'System.Collections.Generic.List<Data.Cases>'

I have not been able to find a good example to help me. How can I achieve this?

    public List<Case> GetAllCases()
    {
        var result = (from c in _Context.Cases
                     join s in _Context.CaseStatus on c.CaseStatusId 
                     equals s.CaseStatusId
                     select new { c.CaseId, c.CaseStatu.Status }).ToList();

        return result;
    }

Answer 1

Your return type doesn't match the declared return type List<Case> . When you select new {} , you are actually returning an anonymous object from your linq expression. You can fix it like this:

public List<Case> GetAllCases()
{
    var result = (from c in _Context.Cases
                 join s in _Context.CaseStatus on c.CaseStatusId 
                 equals s.CaseStatusId
                 select new Case { CaseId = c.CaseId, CaseStatus = c.CaseStatu.Status }).ToList();

    return result;
}

Note the new Case{} when selecting your data. You may need to change CaseId and CaseStatus properties to match the actual properties from the Case class.

Update : To Clarify, you would need a Case class that looked minimally like this:

public class Case {
    public int CaseId { get; set; }
    public string CaseStatus { get; set; }
}

Answer 2

I think the problem is in the select statement where you should return objects list of Case:

public List<Case> GetAllCases()
    {
        var result = (from c in _Context.Cases
                     join s in _Context.CaseStatus on c.CaseStatusId 
                     equals s.CaseStatusId
                     select new Case () { CaseId = c.CaseId, CaseStatusId = c.CaseStatusId  }).ToList();

        return result;
}

Answer 3

you are creating list of annonymous type and returning list of case. that is the issue