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[] { , "张三", , DateTime.Now });
         table.Rows.Add(new object[] { , "李四", , DateTime.Now });
         table.Rows.Add(new object[] { , "王五", , 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 = ; id <= ; id++)
                 {
                     customerTable.Rows.Add(
                         new object[] { id, string.Format("customer{0}", id) });
                 }
                 //customerTable.AcceptChanges();

                 // Add another ten rows
                 for (int id = ; id <= ; 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("\n{0}", label);
             if (rows.Length <= )
             {
                 Console.WriteLine("no rows found");
                 return;
             }
             foreach (DataRow row in rows)
             {
                 foreach (DataColumn column in row.Table.Columns)
                 {
                     Console.Write("\t 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);