c# - 如何在不使用模型的情况下使用 Entity Framework 执行原始 SQL 查询？

Question

我正在尝试学习 C# ASP.NET MVC 5。我正在尝试使用 Entity Framework 来完成我所做的一切。

但是，我需要运行原始 SQL 查询并将结果返回到数组中。

这是我到目前为止所做的。

我创建了我的上下文类，它允许我连接到服务器，它还允许我在运行时更改数据库。

这是我的上下文类

using ScripterEngine.Models;
using System;
using System.Collections.Generic;
using System.Data.Common;
using System.Data.Entity;
using System.Data.Entity.Core.EntityClient;
using System.Data.SqlClient;
using System.Linq;
using System.Web;

namespace ScripterEngine.DataAccessLayer
{
    public class BaseContext : DbContext
    {
        protected string connectionName;
        public DbSet<Campaign> Campaign { get; set; }

        /**
         * Created the connection to the server using the giving connection string name
         * 
         * @param connName
         */
        public BaseContext(string connName = "BaseConnection")
            : base(connName)
        {
            connectionName = connName;
        }

        /**
         * Changes the default database
         * 
         * @param databaseName
         */
        public BaseContext setDatabase(string databaseName)
        {
            var connectionString = System.Configuration.ConfigurationManager.ConnectionStrings[connectionName].ConnectionString;

            SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder(connectionString);

            //change the database before creating the new connection
            builder.InitialCatalog = databaseName;

            string sqlConnectionString = builder.ConnectionString;

            return new BaseContext(sqlConnectionString);
        }
    }
}

而这里如何建立联系就是我所做的

BaseContext db1 = new BaseContext("server1");
var db1New = db1.setDatabase("someTableName");
string tableName = "SomeTableName";

var results = db1New.Database.SqlQuery("SELECT LOWER(column_name) AS column_name FROM information_schema.columns WHERE table_name = @tableName", tableName).ToArray();

这会引发错误

The type arguments for method 'System.Data.Entity.Database.SqlQuery(string, params object[])' cannot be inferred from the usage. Try specifying the type arguments explicitly. C:.NET Projects\ScripterEngine\ScripterEngine\Controllers\CampaignController.cs 42 27 ScripterEngine

我怎样才能执行这个原始查询？

Answer 1

指定string作为类型参数。

var results = db1New.Database.SqlQuery<string>("SELECT LOWER(column_name) AS column_name FROM information_schema.columns WHERE table_name = @p0", tableName).ToArray();
                                       ^^^^^^