EF Core 使用空引用执行存储过程

Question

Executing a stored procedure creates this error with EF Core 2.0. I am beside myself with this error. Any pointers?

public class SalesDTO :  BaseEntity
{
    public int SalesID { get; set; }
    [Display(Name = "User")]
    public string SalesRep { get; set; }
    [Display(Name = "Sales Date")]
    public DateTime OrderDate { get; set; }
    public string CustomerName { get; set; }
    public int? CustomerID { get; set; }
    [Display(Name = "Sale Center")]
    public string CenterName { get; set; }
    public int CenterID { get; set; }
    public decimal TotalAmount { get; set; }
    public SalesType SalesType { get; set; }
}

Model class for the stored procedure.

This is my implementation class

public IEnumerable<SalesDTO> GetSales(int centerID, string user)
{
        string salesRep = user ?? "";

        List<SqlParameter> parms = new List<SqlParameter>
        {
            new SqlParameter("@CenterID", centerID),
            new SqlParameter("@SalesRep", salesRep)
        };

        return DataContext.Set<SalesDTO>().FromSql("spSalesList @CenterID, @SalesRep", parms.ToArray())
                 .Select(x => new SalesDTO
                 {
                     Id = x.SalesID,
                     SalesID = x.SalesID,
                     CustomerID = x.CustomerID,
                     CustomerName = x.CustomerName,
                     SalesType = x.SalesType,
                     TotalAmount = x.TotalAmount,
                     SalesRep = x.SalesRep,
                     CenterName = x.CenterName,
                     OrderDate = x.OrderDate,
                     CenterID = x.CenterID
                 }).AsNoTracking().ToList();
    }

This code throws:

NullReferenceException: Object reference not set to an instance of an object.

with this stack trace

However, if I use SQL Server profiler, I can see that the stored procedure successfully executes when I copy what was executed back to SQL Server Management Studio and execute it.

Answer 1

Can you try below code, please.

return DataContext.Set<SalesDTO>().FromSql($"EXECUTE spSalesList {centerID} {salesRep}")
             .Select(x => new SalesDTO
             {
                 Id = x.SalesID,
                 SalesID = x.SalesID,
                 CustomerID = x.CustomerID,
                 CustomerName = x.CustomerName,
                 SalesType = x.SalesType,
                 TotalAmount = x.TotalAmount,
                 SalesRep = x.SalesRep,
                 CenterName = x.CenterName,
                 OrderDate = x.OrderDate,
                 CenterID = x.CenterID
             }).AsNoTracking().ToList();

Meanwhile, it's worthwhile to know the limitations: https://docs.microsoft.com/en-us/ef/core/querying/raw-sql#limitations

Answer 2

I just realized that the repository works alright it's just the data resolution.

If you use one property in the .Select to match to 2 different properties, the NULL Reference error is generated. So this

return DataContext.Set<SalesDTO>().FromSql("spSalesList @CenterID, @SalesRep, @DateFrom, @DateTo", parms.ToArray())
                 .Select(x => new SalesDTO
                 {
                     Id = x.SalesID,
                     SalesID = x.SalesID,
                     CustomerID = x.CustomerID,
                     CustomerName = x.CustomerName,
                     SalesType = x.SalesType,
                     TotalAmount = x.TotalAmount,
                     SalesRep = x.SalesRep,
                     CenterName = x.CenterName,
                     OrderDate = x.OrderDate,
                     CenterID = x.CenterID
                 }).AsNoTracking().ToList();

will give a Null Reference error because the SalesID is matched to both the SalesID column as well as the Id Column, though it may be the same field. When you however change the code to

return DataContext.Set<SalesDTO>().FromSql("spSalesList @CenterID, @SalesRep, @DateFrom, @DateTo", parms.ToArray())
                 .Select(x => new SalesDTO
                 {
                     Id = x.Id,
                     SalesID = x.SalesID,
                     CustomerID = x.CustomerID,
                     CustomerName = x.CustomerName,
                     SalesType = x.SalesType,
                     TotalAmount = x.TotalAmount,
                     SalesRep = x.SalesRep,
                     CenterName = x.CenterName,
                     OrderDate = x.OrderDate,
                     CenterID = x.CenterID
                 }).AsNoTracking().ToList();

Then it works correctly since the Id and SalesID matches to different fields. I am yet to understand why that is so. I will add a comment when i get to understand.