C# DataTable 类使用

命名空间:

System.Data

程序集:

System.Data.Common.dll

参考连接：https://docs.microsoft.com/zh-cn/dotnet/api/system.data.datatable?view=netcore-3.1

下面示例显示如何创建两个DataTable，并将他们添加到DataSet中

using System;
    using System.Data;
    class Program
    {
        static void Main(string[] args)
        {
            // Create two tables and add them into the DataSet
            DataTable orderTable = CreateOrderTable();
            DataTable orderDetailTable = CreateOrderDetailTable();
            DataSet salesSet = new DataSet();
            salesSet.Tables.Add(orderTable);
            salesSet.Tables.Add(orderDetailTable);

            // Set the relations between the tables and create the related constraint.
            salesSet.Relations.Add("OrderOrderDetail", orderTable.Columns["OrderId"], orderDetailTable.Columns["OrderId"], true);

            Console.WriteLine("After creating the foreign key constriant, you will see the following error if inserting order detail with the wrong OrderId: ");
            try
            {
                DataRow errorRow = orderDetailTable.NewRow();
                errorRow[0] = 1;
                errorRow[1] = "O0007";
                orderDetailTable.Rows.Add(errorRow);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            Console.WriteLine();

            // Insert the rows into the table
            InsertOrders(orderTable);
            InsertOrderDetails(orderDetailTable);

            Console.WriteLine("The initial Order table.");
            ShowTable(orderTable);

            Console.WriteLine("The OrderDetail table.");
            ShowTable(orderDetailTable);

            // Use the Aggregate-Sum on the child table column to get the result.
            DataColumn colSub = new DataColumn("SubTotal", typeof(Decimal), "Sum(Child.LineTotal)");
            orderTable.Columns.Add(colSub);

            // Compute the tax by referencing the SubTotal expression column.
            DataColumn colTax = new DataColumn("Tax", typeof(Decimal), "SubTotal*0.1");
            orderTable.Columns.Add(colTax);

            // If the OrderId is 'Total', compute the due on all orders; or compute the due on this order.
            DataColumn colTotal = new DataColumn("TotalDue", typeof(Decimal), "IIF(OrderId='Total',Sum(SubTotal)+Sum(Tax),SubTotal+Tax)");
            orderTable.Columns.Add(colTotal);

            DataRow row = orderTable.NewRow();
            row["OrderId"] = "Total";
            orderTable.Rows.Add(row);

            Console.WriteLine("The Order table with the expression columns.");
            ShowTable(orderTable);

            Console.WriteLine("Press any key to exit.....");
            Console.ReadKey();
        }

        private static DataTable CreateOrderTable()
        {
            DataTable orderTable = new DataTable("Order");

            // Define one column.
            DataColumn colId = new DataColumn("OrderId", typeof(String));
            orderTable.Columns.Add(colId);

            DataColumn colDate = new DataColumn("OrderDate", typeof(DateTime));
            orderTable.Columns.Add(colDate);

            // Set the OrderId column as the primary key.
            orderTable.PrimaryKey = new DataColumn[] { colId };

            return orderTable;
        }

        private static DataTable CreateOrderDetailTable()
        {
            DataTable orderDetailTable = new DataTable("OrderDetail");

            // Define all the columns once.
            DataColumn[] cols ={
                                  new DataColumn("OrderDetailId",typeof(Int32)),
                                  new DataColumn("OrderId",typeof(String)),
                                  new DataColumn("Product",typeof(String)),
                                  new DataColumn("UnitPrice",typeof(Decimal)),
                                  new DataColumn("OrderQty",typeof(Int32)),
                                  new DataColumn("LineTotal",typeof(Decimal),"UnitPrice*OrderQty")
                              };

            orderDetailTable.Columns.AddRange(cols);
            orderDetailTable.PrimaryKey = new DataColumn[] { orderDetailTable.Columns["OrderDetailId"] };
            return orderDetailTable;
        }

        private static void InsertOrders(DataTable orderTable)
        {
            // Add one row once.
            DataRow row1 = orderTable.NewRow();
            row1["OrderId"] = "O0001";
            row1["OrderDate"] = new DateTime(2013, 3, 1);
            orderTable.Rows.Add(row1);

            DataRow row2 = orderTable.NewRow();
            row2["OrderId"] = "O0002";
            row2["OrderDate"] = new DateTime(2013, 3, 12);
            orderTable.Rows.Add(row2);

            DataRow row3 = orderTable.NewRow();
            row3["OrderId"] = "O0003";
            row3["OrderDate"] = new DateTime(2013, 3, 20);
            orderTable.Rows.Add(row3);
        }

        private static void InsertOrderDetails(DataTable orderDetailTable)
        {
            // Use an Object array to insert all the rows .
            // Values in the array are matched sequentially to the columns, based on the order in which they appear in the table.
            Object[] rows = {
                                 new Object[]{1,"O0001","Mountain Bike",1419.5,36},
                                 new Object[]{2,"O0001","Road Bike",1233.6,16},
                                 new Object[]{3,"O0001","Touring Bike",1653.3,32},
                                 new Object[]{4,"O0002","Mountain Bike",1419.5,24},
                                 new Object[]{5,"O0002","Road Bike",1233.6,12},
                                 new Object[]{6,"O0003","Mountain Bike",1419.5,48},
                                 new Object[]{7,"O0003","Touring Bike",1653.3,8},
                             };

            foreach (Object[] row in rows)
            {
                orderDetailTable.Rows.Add(row);
            }
        }

        private static void ShowTable(DataTable table)
        {
            foreach (DataColumn col in table.Columns)
            {
                Console.Write("{0,-14}", col.ColumnName);
            }
            Console.WriteLine();

            foreach (DataRow row in table.Rows)
            {
                foreach (DataColumn col in table.Columns)
                {
                    if (col.DataType.Equals(typeof(DateTime)))
                        Console.Write("{0,-14:d}", row[col]);
                    else if (col.DataType.Equals(typeof(Decimal)))
                        Console.Write("{0,-14:C}", row[col]);
                    else
                        Console.Write("{0,-14}", row[col]);
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }