DataTable 相关

1、对表的初始化

　　　　　//创建表
        DataTable table = new DataTable();
        //添加列
        table.Columns.Add("ID", typeof(Int32));
        table.Columns.Add("Name", typeof(String));
        table.Columns.Add("Age", typeof(Int32));
        table.Columns.Add("CreateTime", typeof(DateTime));
        //添加行和数据
        table.Rows.Add(new object[] { 1, "张三", 20, DateTime.Now });
        table.Rows.Add(new object[] { 2, "李四", 25, DateTime.Now });
        table.Rows.Add(new object[] { 3, "王五", 30, DateTime.Now });

 2、添加列的一种方式

  　　　　　　DataColumn column;
            // Create new DataColumn, set DataType, 
            // ColumnName and add to DataTable.    
            column = new DataColumn();
            column.DataType = System.Type.GetType("System.Int32");
            column.ColumnName = "id";
            column.ReadOnly = true;
            column.Unique = true;
            // Add the Column to the DataColumnCollection.
            table.Columns.Add(column);

 3、 DataViewRowState.Added 与 Datatable.AcceptChanges() 的一点关系

先上一段MSDN的实例代码。

Select(String, String, DataViewRowState)

 static void Main(string[] args)
        {
            try
            {
                DataTable customerTable = new DataTable("Customers");
                // Add columns
                customerTable.Columns.Add("id", typeof(int));
                customerTable.Columns.Add("name", typeof(string));

                // Set PrimaryKey
                customerTable.Columns["id"].Unique = true;
                customerTable.PrimaryKey = new DataColumn[]
                    { customerTable.Columns["id"] };

                // Add ten rows
                for (int id = 1; id <= 10; id++)
                {
                    customerTable.Rows.Add(
                        new object[] { id, string.Format("customer{0}", id) });
                }
                //customerTable.AcceptChanges();

                // Add another ten rows
                for (int id = 11; id <= 20; id++)
                {
                    customerTable.Rows.Add(
                        new object[] { id, string.Format("customer{0}", id) });
                }
                customerTable.AcceptChanges();

                string expression;
                string sortOrder;

                expression = "id > 5";
                // Sort descending by column named CompanyName.
                sortOrder = "name DESC";
                // Use the Select method to find all rows matching the filter.
                DataRow[] foundRows =
                    customerTable.Select(expression, sortOrder,
                    DataViewRowState.Added);

                PrintRows(foundRows, "filtered rows");

                foundRows = customerTable.Select();
                PrintRows(foundRows, "all rows");

                Console.WriteLine("OK");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }

            Console.ReadKey();
        }
        private static void PrintRows(DataRow[] rows, string label)
        {
            Console.WriteLine("
{0}", label);
            if (rows.Length <= 0)
            {
                Console.WriteLine("no rows found");
                return;
            }
            foreach (DataRow row in rows)
            {
                foreach (DataColumn column in row.Table.Columns)
                {
                    Console.Write("	 table {0}", row[column]);
                }
                Console.WriteLine();
            }
        }

　当使用 AcceptChanges 方法后，之前对datatable的 Added、Modified、Unchanged、Deleted 都会被提交。比如下面这一行中 select 将检测不到 AcceptChanges之前的对表的增加。 

 DataRow[] foundRows =customerTable.Select(expression, sortOrder,DataViewRowState.Added);