实体框架核心-一种用于多个查询的模型

Question

I have a .NET Core API using Entity Framework Core. We use .FromSQL() to execute stored procedures. The problem I'm having is we have two queries that return Account information - one for a single account and one for a paged list of accounts.

The account list returns a column for RowCount which the single account query does not return, so now the single account query returns an error ( Rowcount returns the total number of accounts in the database, not just the accounts on the requested page so you know how many pages of data there are).

The error:

The required column 'RowCount' was not present in the results of a 'FromSql' operation

Here is the model

public class Account
{
    [Key]
    public long AccountId { get; set; }

    public string AccountName { get; set; }
    public bool IsDeleted { get; set; }
    public int RowCount { get; set; }

    [NotMapped]
    public bool Found => AccountId > 0;
}

And our dbContext

public class AccountDbContext : DbContext
{
    private DbSet<Account> TAccount { get; set; }

    public AccountDbContext(DbContextOptions<AccountDbContext> options) : base(options)
    {
    }

    public Account GetAccountById(long accountId)
    {
        var pAccount = new SqlParameter("accountId", accountId);
        Account account = TAccount.FromSql("EXEC dbo.SPR_Account_GetById @accountId", pAccount).FirstOrDefault();
        return account;
    }

    public List<Account> GetAccounts(int offset, int limit)
    {
        var pOffset = new SqlParameter("offset", offset);
        var pLimit = new SqlParameter("limit", limit);

        var dataSet = TAccount.FromSql($"EXEC dbo.SPR_Account_GetAll @offset=@offset,@limit=@limit", pOffset, pLimit).ToList();

        return dataSet;
    }
}

My question: is there a way to reuse this model for both queries? I think it's dumb to create a second model with identical properties. And I can never get entity to play nice with inheritance. It always gives me an error about Discrimitator not being found.

Answer 1

Thanks to Chris Pratt and Dennis1679, I looked further into inheritance. Entity Framework doesn't like it when both a base class and derived class are registered as queryable types. I created a base class with the common properties and two derived classes: one for the single account and one for the list that includes the RowCount property. I'm not 100% happy with the fake inheritance, but I don't have to return a dummy RowCount from the stored proc and I don't have to duplicate my object.

public class AccountBase
{
    [Key]
    public long AccountId { get; set; }

    public string AccountName { get; set; }
    public bool IsDeleted { get; set; }

    [NotMapped]
    public bool Found => AccountId > 0;
}

public class AccountDataModel : AccountBase
{
}

public class AccountCount : AccountBase
{
   public int RowCount { get; set; }
}

Then, in my dbContext:

public class AccountDbContext : DbContext
{
    private DbSet<AccountDataModel> TAccount { get; set; }
    private DbSet<AccountCount> AccountList { get; set; }

    public AccountDbContext(DbContextOptions<AccountDbContext> options) : base(options)
    {
    }

    public Account GetAccountById(long accountId)
    {
        var pAccount = new SqlParameter("accountId", accountId);
        Account account = TAccount.FromSql("EXEC dbo.SPR_Account_GetById @accountId", pAccount).FirstOrDefault();
        return account;
    }

    public List<Account> GetAccounts(int offset, int limit)
    {
        var pOffset = new SqlParameter("offset", offset);
        var pLimit = new SqlParameter("limit", limit);

        var dataSet = AccountList.FromSql($"EXEC dbo.SPR_Account_GetAll @offset=@offset,@limit=@limit", pOffset, pLimit).ToList();

        return dataSet;
    }
}

Answer 2

In order to use FromSql with an entity, there must be a direct one-to-one correlation between what's returned and the properties on the entity. This is not optional and there is no alternative.

However, if you use a DTO class, you can do whatever you like. You just add it to your context like:

public DbQuery<AccountDTO> AccountDTOs { get; set; }

And then you can use FromSql on that instead, without any of the issues you're having.