使用实体框架 C# 执行通用 SQL 查询

Question

我想执行 sql 查询。然后将检索到的值转储到网页中。我可以在 c# 中使用 SQLCommand。但是我如何使用实体框架来做到这一点。我觉得很难的原因是因为我不知道这个查询将在哪个表上运行（至于这个我将不得不解析选择查询）。请帮帮我。

Answer 1

context.ExecuteStoreQuery<Product>("select * from table where id = {0}", 1);

ExecuteStoreQuery

Answer 2

我意识到已经有一个很好的答案，但我可以给你一个提示 - 你可以实现 Execute Around Method 模式来执行事务中的选择、插入和更新的通用查询。我是这样做的：

internal class CommonDataTool
{
    internal delegate object SqlCommandDelegate();

    /// <summary>
    /// Use only for select where (a) return value(s) is/are expected and/or required
    /// </summary>
    /// <typeparam name="T"> Expected datacontext model return type, example: DataContext.User</typeparam>
    /// <param name="context"> The DataContext (YourDataModel) instance to be used in the transaction </param>
    /// <param name="action"> Linq to Entities action to perform</param>
    /// <returns> Returns an object that can be implicitly casted to List of T where T is the expected return type. Example: List of DataContext.User</returns>
    internal List <T> ExecuteSelect<T>(YourDataModel context, SqlCommandDelegate action)
    {
        using (context)
        {
            var retVal = action(); return ((ObjectQuery<T>)retVal).ToList();
        }
    }

    /// <summary>
    /// Use for updates and inserts where no return value is expected or required
    /// </summary>
    /// <param name="context"> The DataContext (YourDataModel) instance to be used in the transaction </param>
    /// <param name="action"> Linq to Entities action to perform</param>
    internal void ExecuteInsertOrUpdate(YourDataModel context, SqlCommandDelegate action)
    {
        using (context)
        {
            using (var transaction = context.BeginTransaction())
            {
                try
                { action(); context.SaveChanges(); transaction.Commit(); }
                catch (Exception )
                { transaction.Rollback(); throw; }
            }
        }
    }
}

public static class ObjectContextExtensionMethods
{
    public static DbTransaction BeginTransaction( this ObjectContext context)
    {
        if (context.Connection.State != ConnectionState .Open) { context.Connection.Open(); }
        return context.Connection.BeginTransaction();
    }
}

这很好，因为您可以使用简约的 linq 查询实现数据适配器，您可以将其作为委托参数传递：

var users = _dataTool.ExecuteSelect<DataContext.User>(Db, GetUsers);

private static object GetUsers()
{
    return (from u in Db.User select U).ToList();
}

另一个好处是您的更新/插入在事务中运行，而您不必在 linq 查询中显式声明它们。

例子：

public void UpdateUser(DomainUser user)
{
_dataTool.ExecuteInsertOrUpdate(Db, () =>
        {
            Db.User.First(u => u.UserId == user.Id).Email = user.Email;
            Db.User.First(u => u.UserId == user.Id).Name = user.Name;
            Db.User.First(u => u.UserId == user.Id).LastName = user.LastName;
            Db.User.First(u => u.UserId == user.Id).Password = user.Password;
            return null;
        });    
}

源：http://www.marcusnordquist.com/?p=66