从数据读取器填充数据表
我正在做一个基本的东西在C＃（MS VS2008），并有一个比正确的devise比特定的代码更多的问题。
我正在创build一个数据表，然后尝试从一个datareader（这是基于SQL存储过程）加载数据表。 我想知道的是，加载数据表最有效的方法是做一个while语句，或者是否有更好的方法。
对我来说，唯一的缺点是我必须手动input我想添加在我的while语句中的字段，但是我也不知道如何自动执行，因为我不希望SP中的所有字段都只是select字段，但这在我眼里并不是什么大事。
我将代码片段包含在我所做的全部内容之下，但对我来说，代码本身并不显着，甚至不是我所问的。 更多的是对我的方法感到疑惑，如果我的策略是错误的/效率低下的，我会在后面为代码提供帮助。
var dtWriteoffUpload = new DataTable(); dtWriteoffUpload.Columns.Add("Unit"); dtWriteoffUpload.Columns.Add("Year"); dtWriteoffUpload.Columns.Add("Period"); dtWriteoffUpload.Columns.Add("Acct"); dtWriteoffUpload.Columns.Add("Descr"); dtWriteoffUpload.Columns.Add("DEFERRAL_TYPE"); dtWriteoffUpload.Columns.Add("NDC_Indicator"); dtWriteoffUpload.Columns.Add("Mgmt Cd"); dtWriteoffUpload.Columns.Add("Prod"); dtWriteoffUpload.Columns.Add("Node"); dtWriteoffUpload.Columns.Add("Curve_Family"); dtWriteoffUpload.Columns.Add("Sum Amount"); dtWriteoffUpload.Columns.Add("Base Curr"); dtWriteoffUpload.Columns.Add("Ledger"); cmd = util.SqlConn.CreateCommand(); cmd.CommandTimeout = 1000; cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText = "proc_writeoff_data_details"; cmd.Parameters.Add("@whoAmI", SqlDbType.VarChar).Value = WindowsIdentity.GetCurrent().Name; cmd.Parameters.Add("@parmEndDateKey", SqlDbType.VarChar).Value = myMostRecentActualDate; cmd.Parameters.Add("@countrykeys", SqlDbType.VarChar).Value = myCountryKey; cmd.Parameters.Add("@nodekeys", SqlDbType.VarChar).Value = "1,2"; break; dr = cmd.ExecuteReader(); while (dr.Read()) { dtWriteoffUpload.Rows.Add(dr["country name"].ToString(), dr["country key"].ToString()); } 您可以使用接受IDataReader的Load()方法直接从数据读取器加载DataTable 。
var dataReader = cmd.ExecuteReader(); var dataTable = new DataTable(); dataTable.Load(dataReader);
请检查下面的代码。 自动将它转换为DataTable
private void ConvertDataReaderToTableManually() { SqlConnection conn = null; try { string connString = ConfigurationManager.ConnectionStrings["NorthwindConn"].ConnectionString; conn = new SqlConnection(connString); string query = "SELECT * FROM Customers"; SqlCommand cmd = new SqlCommand(query, conn); conn.Open(); SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection); DataTable dtSchema = dr.GetSchemaTable(); DataTable dt = new DataTable(); // You can also use an ArrayList instead of List<> List<DataColumn> listCols = new List<DataColumn>(); if (dtSchema != null) { foreach (DataRow drow in dtSchema.Rows) { string columnName = System.Convert.ToString(drow["ColumnName"]); DataColumn column = new DataColumn(columnName, (Type)(drow["DataType"])); column.Unique = (bool)drow["IsUnique"]; column.AllowDBNull = (bool)drow["AllowDBNull"]; column.AutoIncrement = (bool)drow["IsAutoIncrement"]; listCols.Add(column); dt.Columns.Add(column); } } // Read rows from DataReader and populate the DataTable while (dr.Read()) { DataRow dataRow = dt.NewRow(); for (int i = 0; i < listCols.Count; i++) { dataRow[((DataColumn)listCols[i])] = dr[i]; } dt.Rows.Add(dataRow); } GridView2.DataSource = dt; GridView2.DataBind(); } catch (SqlException ex) { // handle error } catch (Exception ex) { // handle error } finally { conn.Close(); } }
如果您正在尝试加载DataTable ，请改用SqlDataAdapter ：
DataTable dt = new DataTable(); using (SqlConnection c = new SqlConnection(cString)) using (SqlDataAdapter sda = new SqlDataAdapter(sql, c)) { sda.SelectCommand.CommandType = CommandType.StoredProcedure; sda.SelectCommand.Parameters.AddWithValue("@parm1", val1); ... sda.Fill(dt); }
你甚至不需要定义列。 只需创buildDataTable并Fill它。
在这里， cString是你的连接string， sql是存储过程命令。
正如Sagi在他们的回答DataTable.Load中所说的是一个很好的解决scheme。 如果您试图从一个阅读器加载多个表，则不需要调用DataReader.NextResult。 DataTable.Load方法也将读者推进到下一个结果集（如果有的话）。
// Read every result set in the data reader. while (!reader.IsClosed) { DataTable dt = new DataTable(); // DataTable.Load automatically advances the reader to the next result set dt.Load(reader); items.Add(dt); }
我也考虑到了这一点，在比较SqlDataAdaptor.Fill方法和SqlDataReader.Load函数之后，我发现SqlDataAdaptor.Fill方法的速度是我用过的结果集的两倍多
使用的代码：
[TestMethod] public void SQLCommandVsAddaptor() { long adaptorFillLargeTableTime, readerLoadLargeTableTime, adaptorFillMediumTableTime, readerLoadMediumTableTime, adaptorFillSmallTableTime, readerLoadSmallTableTime, adaptorFillTinyTableTime, readerLoadTinyTableTime; string LargeTableToFill = "select top 10000 * from FooBar"; string MediumTableToFill = "select top 1000 * from FooBar"; string SmallTableToFill = "select top 100 * from FooBar"; string TinyTableToFill = "select top 10 * from FooBar"; using (SqlConnection sconn = new SqlConnection("Data Source=.;initial catalog=Foo;persist security info=True; user id=bar;password=foobar;")) { // large data set measurements adaptorFillLargeTableTime = MeasureExecutionTimeMethod(sconn, LargeTableToFill, ExecuteDataAdapterFillStep); readerLoadLargeTableTime = MeasureExecutionTimeMethod(sconn, LargeTableToFill, ExecuteSqlReaderLoadStep); // medium data set measurements adaptorFillMediumTableTime = MeasureExecutionTimeMethod(sconn, MediumTableToFill, ExecuteDataAdapterFillStep); readerLoadMediumTableTime = MeasureExecutionTimeMethod(sconn, MediumTableToFill, ExecuteSqlReaderLoadStep); // small data set measurements adaptorFillSmallTableTime = MeasureExecutionTimeMethod(sconn, SmallTableToFill, ExecuteDataAdapterFillStep); readerLoadSmallTableTime = MeasureExecutionTimeMethod(sconn, SmallTableToFill, ExecuteSqlReaderLoadStep); // tiny data set measurements adaptorFillTinyTableTime = MeasureExecutionTimeMethod(sconn, TinyTableToFill, ExecuteDataAdapterFillStep); readerLoadTinyTableTime = MeasureExecutionTimeMethod(sconn, TinyTableToFill, ExecuteSqlReaderLoadStep); } using (StreamWriter writer = new StreamWriter("result_sql_compare.txt")) { writer.WriteLine("10000 rows"); writer.WriteLine("Sql Data Adapter 100 times table fill speed 10000 rows: {0} milliseconds", adaptorFillLargeTableTime); writer.WriteLine("Sql Data Reader 100 times table load speed 10000 rows: {0} milliseconds", readerLoadLargeTableTime); writer.WriteLine("1000 rows"); writer.WriteLine("Sql Data Adapter 100 times table fill speed 1000 rows: {0} milliseconds", adaptorFillMediumTableTime); writer.WriteLine("Sql Data Reader 100 times table load speed 1000 rows: {0} milliseconds", readerLoadMediumTableTime); writer.WriteLine("100 rows"); writer.WriteLine("Sql Data Adapter 100 times table fill speed 100 rows: {0} milliseconds", adaptorFillSmallTableTime); writer.WriteLine("Sql Data Reader 100 times table load speed 100 rows: {0} milliseconds", readerLoadSmallTableTime); writer.WriteLine("10 rows"); writer.WriteLine("Sql Data Adapter 100 times table fill speed 10 rows: {0} milliseconds", adaptorFillTinyTableTime); writer.WriteLine("Sql Data Reader 100 times table load speed 10 rows: {0} milliseconds", readerLoadTinyTableTime); } Process.Start("result_sql_compare.txt"); } private long MeasureExecutionTimeMethod(SqlConnection conn, string query, Action<SqlConnection, string> Method) { long time; // know C# // execute single read step outside measurement time, to warm up cache or whatever Method(conn, query); // start timing time = Environment.TickCount; for (int i = 0; i < 100; i++) { Method(conn, query); } // return time in milliseconds return Environment.TickCount - time; } private void ExecuteDataAdapterFillStep(SqlConnection conn, string query) { DataTable tab = new DataTable(); conn.Open(); using (SqlDataAdapter comm = new SqlDataAdapter(query, conn)) { // adaptor fill table function comm.Fill(tab); } conn.Close(); } private void ExecuteSqlReaderLoadStep(SqlConnection conn, string query) { DataTable tab = new DataTable(); conn.Open(); using (SqlCommand comm = new SqlCommand(query, conn)) { using (SqlDataReader reader = comm.ExecuteReader()) { // IDataReader Load function tab.Load(reader); } } conn.Close(); }
结果：
10000行：
Sql Data Adapter 100次表填充速度10000行：11782毫秒
Sql数据读取器100次表加载速度10000行：26047毫秒
1000行：
Sql Data Adapter 100倍表填充速度1000行：984毫秒
Sql Data Reader 100倍表加载速度1000行：2031毫秒
100行：
Sql Data Adapter 100倍表填充速度100行：125毫秒
Sql Data Reader 100倍表加载速度100行：235毫秒
10行：
Sql Data Adapter 100倍表填充速度10行：32毫秒
Sql Data Reader 100倍表加载速度10行：93毫秒
对于性能问题，使用SqlDataAdaptor.Fill方法效率更高。 所以除非你想用自己的脚拍自己的脚 它对于小型和大型数据集运行速度更快
