Question

我必须使用C＃将列表传递给SQL Server查询。我的代码在这里：

using (SqlDataReader _myReader_2 = _myCommand_3.ExecuteReader())
{
    _Node_Neighbor.Clear();
        while (_myReader_2.Read())
        {
            _Node_Neighbor.Add(Convert.ToInt32(_myReader_2["Target_Node"]));
        }

    _myReader_2.Close();

  //Here I have to pass this _Node_Neighbor i.e. of type List<int> to another  
  //SQL Server query as:

    try
        {
            SqlCommand _myCommand_4 = _con.CreateCommand();

            _myCommand_4.CommandText = @"SELECT COUNT(*) FROM GraphEdges
                                         WHERE Source_Node IN @Source_Node 
                                         AND Target_Node IN @Target_Node";

            _myCommand_4.Parameters.AddWithValue("@Source_Node", _Node_Neighbor);
            _myCommand_4.Parameters.AddWithValue("@Target_Node", _Node_Neighbor);

            _Mutual_Links = Convert.ToInt32(_myCommand_4.ExecuteScalar());
        }
        catch(Exception e)
        {
            Console.WriteLine(e.Message);
        }
}

然而，要将列表作为参数传递，我认为可能还有其他一些方法，这就是我收到此错误的原因： No mapping exists from object type Systems.Collections.Generic.List

谢谢！

Answer 1

为了传递IN的数组/列表，您必须为列表中的每个值创建一个参数。

try
    {
        SqlCommand _myCommand_4 = _con.CreateCommand();


        List<string> sqlParams = new List<string>();
        int i = 0;
        foreach(var value in _Node_Neighbor){
            var name = "@p"  + i++;
            _myCommand_4.Parameters.Add(name,value);
            sqlParams.Add(name);
        }

        string paramNames = string.Join(",", sqlParams);

        _myCommand_4.CommandText = "SELECT COUNT(*) FROM GraphEdges"
                       " WHERE Source_Node IN (" + paramNames + ") " 
                         " AND Target_Node IN (" + paramNames + ")";


        _Mutual_Links = Convert.ToInt32(_myCommand_4.ExecuteScalar());
    }
    catch(Exception e)
    {
        Console.WriteLine(e.Message);
    }

Answer 2

在sql server中使用用户定义的表格，在ADO.NET代码中使用数据表。

Answer 3

如果数组不大，则在c＃中构建动态查询

using (SqlDataReader _myReader_2 = _myCommand_3.ExecuteReader())
        {
            _Node_Neighbor.Clear();
            while (_myReader_2.Read())
            {
                _Node_Neighbor.Add(Convert.ToInt32(_myReader_2["Target_Node"]));
            }

            _myReader_2.Close();

            //Here I have to pass this _Node_Neighbor i.e. of type List<int> to another  
            //SQL Server query as:

            try
            {
                var query = @"SELECT COUNT(*) FROM GraphEdges
                WHERE Source_Node IN

                (##Source_Node)

                AND Target_Node IN 
                (##Target_Node)";
                var sourceNode = "";
                foreach (var item in _Node_Neighbor)
                {
                    sourceNode += item + ",";
                }

                sourceNode = sourceNode.TrimEnd(',');

                var targetNode = "";
                foreach (var item in _Node_Neighbor)
                {
                    targetNode += item + ",";
                }

                targetNode = targetNode.TrimEnd(',');

                query = query.Replace("##Source_Node", sourceNode).Replace("##Target_Node", targetNode);

                SqlCommand _myCommand_4 = _con.CreateCommand();

                _myCommand_4.CommandText = @"SELECT COUNT(*) FROM GraphEdges
                                     WHERE Source_Node IN @Source_Node 
                                     AND Target_Node IN @Target_Node";


                _Mutual_Links = Convert.ToInt32(_myCommand_4.ExecuteScalar());
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
        }

将List <int>作为查询参数传递给SQL Server

3 个答案: