如何在 C# 实体框架中获取 SQL 查询的结果？

Question

I'm using WPF, C#, Entity Framework database-first with a SQL Server database.

I could execute this query successfully in SQL Server:

SELECT 
    SUM(MEGHk) AS Meghksm, 
    SUM(MABL_K) AS Mablksm, 
    SUM(N_MOIN) AS N_MOINSM, 
    SUM(IMBAA) AS IMBAAsm 
FROM 
    INVO_LST 
WHERE
    (TAG = 2) AND (NUMBER = 4)

In C# code:

 var quer_Sumfactor5 = dbms.Database.SqlQuery<INVO_LST>("SELECT SUM(MEGHk) AS Meghksm, SUM(MABL_K) AS Mablksm, SUM(N_MOIN) AS N_MOINSM, SUM(IMBAA) AS IMBAAsm FROM INVO_LST WHERE(TAG = 2) AND (NUMBER = " + TextB_Number.Text + ")").ToList();

Which returns this error:

Answer 1

You are performing aggregation on some of the columns in your query and have aliased the results of these aggregations. As a result the columns returned ( Meghksm , Mablksm etc.) are not the same as those in the database table INVO_LST that your C# class INVO_LST is a representation of. So Entity Framework cannot map the results returned to the class that you have specified in your dbms.Database.SqlQuery<INVO_LST> call.

You need to create a class that EF can map to the results of the query:

public class INVO_LST_SUM
{
    public decimal Meghksm {get; set;}
    public decimal Mablksm {get; set;}
    public decimal N_MOINSM {get; set;}
    public decimal IMBAAsm {get; set;}
}

Then you can call:

var quer_Sumfactor5 = dbms.Database.SqlQuery<INVO_LST_SUM>("SELECT SUM(MEGHk) AS Meghksm, SUM(MABL_K) AS Mablksm, SUM(N_MOIN) AS N_MOINSM, SUM(IMBAA) AS IMBAAsm FROM INVO_LST WHERE(TAG = 2) AND (NUMBER = " + TextB_Number.Text + ")").ToList();

(although please carefully note @Liam 's comment re SQL injection...)

Answer 2

first of all you should read the sql injection. You should not use the " TextB_Number.Text " in your query, as it can result in less data security. Secondly, dbms.Database.SqlQuery<INVO_LST> SqLQuery expects a class that can match the type and name of the columns that will come in query result. So you should use following approach.

public class INVO_LST_SUM
{
   public decimal Meghksm {get; set;}
   public decimal Mablksm {get; set;}
   public decimal N_MOINSM {get; set;}
   public decimal IMBAAsm {get; set;}
}

and

var quer_Sumfactor5 = dbms.Database.SqlQuery<INVO_LST_SUM>("SELECT SUM(MEGHk) AS Meghksm, SUM(MABL_K) AS Mablksm, SUM(N_MOIN) AS N_MOINSM, SUM(IMBAA) AS IMBAAsm FROM INVO_LST WHERE(TAG = 2) AND (NUMBER = " + TextB_Number.Text + ")").ToList();

Use decimal instead of int,, As the aggregate function Sum can results in Decimal value also.