使用实体框架返回数据表

Question

我正在使用实体框架。在我的应用程序中有一种特殊情况，我必须使用存储过程。由于SP中写了很多SQL语句，我不想​​在我的C#代码中重写它。我只需要以数据表的形式返回结果。我已经写了一点代码，但我被困在一个点上。有人可以完成下面的代码吗？

using (dbContext.Database.Connection)
{
dbContext.Database.Connection.Open();
DbCommand cmdItems= dbContext.Database.Connection.CreateCommand();
cmdItems.CommandText = "GetAvailableItems";
cmdItems.CommandType = CommandType.StoredProcedure;
cmdItems.Parameters.Add(new SqlParameter("jobCardId", 100525));
//Need to write code below to populate a DataTable.
}

Answer 1

我只是混淆了答案。此代码运行动态查询并将结果转换为字典列表。

public List < Dictionary < string,object >> DataTableToDictionaryList(DataTable table) {
    List < Dictionary < string,
    object >> parentRow = new List < Dictionary < string,
    object >> ();
    Dictionary < string,
    object > childRow;
    foreach(DataRow row in table.Rows) {
        childRow = new Dictionary < string,
        object > ();
        foreach(DataColumn col in table.Columns) {
            childRow.Add(col.ColumnName, row[col]);
        }
        parentRow.Add(childRow);
    }
    return (parentRow);
}

List < Dictionary < string,object >> RunDynamicQuery(string sql, Dictionary < string, Object > parameters = null, int resultSet = 0, CommandType commandType = CommandType.Text) {
    // creates resulting dataset
    var resultDataSet = new DataSet();

    // creates a data access context (DbContext descendant)
    using(var context = new DataDbContext()) {
        // creates a Command 
        var conn = context.Database.Connection;
        var cmd = conn.CreateCommand();
        cmd.CommandType = commandType;
        cmd.CommandText = sql;

        if (parameters != null) {
            // adds all parameters
            foreach(var pr in parameters) {
                var p = cmd.CreateParameter();
                p.ParameterName = pr.Key;
                p.Value = pr.Value;
                cmd.Parameters.Add(p);
            }
        }

        try {
            // executes
            if (conn.State != ConnectionState.Open) {
                conn.Open();
            }

            var reader = cmd.ExecuteReader();

            // loop through all resultsets (considering that it's possible to have more than one)
            int currentResultSet = -1;
            do {
                currentResultSet++;
                //skip lower resultsets
                if (resultSet > currentResultSet) {
                    continue;
                }

                // loads the DataTable (schema will be fetch automatically)
                var tb = new DataTable();
                tb.Load(reader);
                resultDataSet.Tables.Add(tb);
                //make sure to get only one result set
                break;
            } while (! reader . IsClosed );

        }
        finally {
            // closes the connection
            context.Database.Connection.Close();
        }
    }

    return DataTableToDictionaryList(resultDataSet.Tables[0]);
}

Answer 2

非常感谢各位。我解决了。这是解决方案：

using (var context = new DataBaseContext())
{
    var dt = new DataTable();
    var conn = context.Database.Connection;
    var connectionState = conn.State;
    try
    {
        if (connectionState != ConnectionState.Open) conn.Open();
        using (var cmd = conn.CreateCommand())
        {
            cmd.CommandText = "GetAvailableItems";
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add(new SqlParameter("jobCardId", 100525));
            using (var reader = cmd.ExecuteReader())
            {
                dt.Load(reader);
            }
        }
    }
    catch (Exception ex)
    {
        // error handling
        throw;
    }
    finally
    {
        if (connectionState != ConnectionState.Closed) conn.Close();
    }
    return dt;
}

Answer 3

此示例将返回一个datatable 对象，从EntityFramework 中选择数据。

我相信这是实现目标的最佳解决方案。但是，此解决方案的问题在于枚举了每条记录。您可能希望先过滤列表，然后从列表中运行它以避免这种情况。

DataTable dt = new DataTable();
(from rec in database.Table.AsEnumerable()
                     select new
                     {
                         id = rec.id,
                         name = rec.Name
                         //etc
                     }).Aggregate(table, (dt, r) =>
                     {
                         dt.Rows.Add(r.id, r.Name);
                         return dt;
                     });

Answer 4

此解决方案简单、快速且易于使用。

创建一个 DbContext 扩展：

using System.Data;
using System.Data.Common;
using System.Data.Entity;
..
..
public static class DbContextExtensions
{
    public static DataTable DataTable(this DbContext context, string sqlQuery)
    {
        DbProviderFactory dbFactory = DbProviderFactories.GetFactory(context.Database.Connection);

        using (var cmd = dbFactory.CreateCommand())
        {
            cmd.Connection = context.Database.Connection;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = sqlQuery;
            using (DbDataAdapter adapter = dbFactory.CreateDataAdapter())
            {
                adapter.SelectCommand = cmd;

                DataTable dt = new DataTable();
                adapter.Fill(dt);

                return dt;
            }
        }
    }
}

例子：

using (MyDbContext db = new MyDbContext())
{
    string query = db.Students.Where(o => o.Age > 20).ToString();

    DataTable dataTable = db.DataTable(query);

    ..

    DataTable dt = db.DataTable(
                         (  from o in db.Studets
                            where o.Age > 20
                            select o
                         ).ToString()
                    );
}

Answer 5

只是改进了以前的解决方案，现在包括通用参数（不是特定于 SQL Server）和多个结果集支持：

    DataSet GetDataSet(string sql, CommandType commandType, Dictionary<string, Object> parameters)
    {
        // creates resulting dataset
        var result = new DataSet();

        // creates a data access context (DbContext descendant)
        using (var context = new MyDbContext())
        {
            // creates a Command 
            var cmd = context.Database.Connection.CreateCommand();
            cmd.CommandType = commandType;
            cmd.CommandText = sql;

            // adds all parameters
            foreach (var pr in parameters)
            {
                var p = cmd.CreateParameter();
                p.ParameterName = pr.Key;
                p.Value = pr.Value;
                cmd.Parameters.Add(p);
            }

            try
            {
                // executes
                context.Database.Connection.Open();
                var reader = cmd.ExecuteReader();

                // loop through all resultsets (considering that it's possible to have more than one)
                do
                {
                    // loads the DataTable (schema will be fetch automatically)
                    var tb = new DataTable();
                    tb.Load(reader);
                    result.Tables.Add(tb);

                } while (!reader.IsClosed);
            }
            finally
            {
                // closes the connection
                context.Database.Connection.Close();
            }
        }

        // returns the DataSet
        return result;
    }