極客書

ADO.NET

ADO.NET提供了前端控制項和後端資料庫之間的橋樑。NET對象封裝了所有的數據訪問操作，控制項與這些對象交互以顯示數據，從而隱藏了數據移動的細節。

下圖顯示了ADO.NET對象：

ADO.Net objects

The DataSet Class

數據集表示資料庫的一個子集。它沒有到資料庫的連續連接。要更新資料庫，需要重新連接。數據集包含數據表對象和數據關係對象。DataRelation對象表示兩個表之間的關係。

下表顯示了數據集類的一些重要屬性：

Properties Description
CaseSensitive Indicates whether string comparisons within the data tables are case-sensitive.
Container Gets the container for the component.
DataSetName Gets or sets the name of the current data set.
DefaultViewManager Returns a view of data in the data set.
DesignMode Indicates whether the component is currently in design mode.
EnforceConstraints Indicates whether constraint rules are followed when attempting any update operation.
Events Gets the list of event handlers that are attached to this component.
ExtendedProperties Gets the collection of customized user information associated with the DataSet.
HasErrors Indicates if there are any errors.
IsInitialized Indicates whether the DataSet is initialized.
Locale Gets or sets the locale information used to compare strings within the table.
Namespace Gets or sets the namespace of the DataSet.
Prefix Gets or sets an XML prefix that aliases the namespace of the DataSet.
Relations Returns the collection of DataRelation objects.
Tables Returns the collection of DataTable objects.

下表顯示了數據集類的一些重要方法：

Methods Description
AcceptChanges Accepts all changes made since the DataSet was loaded or this method was called.
BeginInit Begins the initialization of the DataSet. The initialization occurs at run time.
Clear Clears data.
Clone Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
Copy Copies both structure and data.
CreateDataReader() Returns a DataTableReader with one result set per DataTable, in the same sequence as the tables appear in the Tables collection.
CreateDataReader(DataTable[]) Returns a DataTableReader with one result set per DataTable.
EndInit Ends the initialization of the data set.
Equals(Object) Determines whether the specified Object is equal to the current Object.
Finalize Free resources and perform other cleanups.
GetChanges Returns a copy of the DataSet with all changes made since it was loaded or the AcceptChanges method was called.
GetChanges(DataRowState) Gets a copy of DataSet with all changes made since it was loaded or the AcceptChanges method was called, filtered by DataRowState.
GetDataSetSchema Gets a copy of XmlSchemaSet for the DataSet.
GetObjectData Populates a serialization information object with the data needed to serialize the DataSet.
GetType Gets the type of the current instance.
GetXML Returns the XML representation of the data.
GetXMLSchema Returns the XSD schema for the XML representation of the data.
HasChanges() Gets a value indicating whether the DataSet has changes, including new, deleted, or modified rows.
HasChanges(DataRowState) Gets a value indicating whether the DataSet has changes, including new, deleted, or modified rows, filtered by DataRowState.
IsBinarySerialized Inspects the format of the serialized representation of the DataSet.
Load(IDataReader, LoadOption, DataTable[]) Fills a DataSet with values from a data source using the supplied IDataReader, using an array of DataTable instances to supply the schema and namespace information.
Load(IDataReader, LoadOption, String[]) Fills a DataSet with values from a data source using the supplied IDataReader, using an array of strings to supply the names for the tables within the DataSet.
Merge() Merges the data with data from another DataSet. This method has different overloaded forms.
ReadXML() Reads an XML schema and data into the DataSet. This method has different overloaded forms.
ReadXMLSchema(0) Reads an XML schema into the DataSet. This method has different overloaded forms.
RejectChanges Rolls back all changes made since the last call to AcceptChanges.
WriteXML() Writes an XML schema and data from the DataSet. This method has different overloaded forms.
WriteXMLSchema() Writes the structure of the DataSet as an XML schema. This method has different overloaded forms.

The DataTable Class

DataTable類表示資料庫中的表。它具有以下重要屬性;這些屬性中的大多數是只讀屬性，PrimaryKey屬性除外：

Properties Description
ChildRelations Returns the collection of child relationship.
Columns Returns the Columns collection.
Constraints Returns the Constraints collection.
DataSet Returns the parent DataSet.
DefaultView Returns a view of the table.
ParentRelations Returns the ParentRelations collection.
PrimaryKey Gets or sets an array of columns as the primary key for the table.
Rows Returns the Rows collection.

下表顯示了DataTable類的一些重要方法：

Methods Description
AcceptChanges Commits all changes since the last AcceptChanges.
Clear Clears all data from the table.
GetChanges Returns a copy of the DataTable with all changes made since the AcceptChanges method was called.
GetErrors Returns an array of rows with errors.
ImportRows Copies a new row into the table.
LoadDataRow Finds and updates a specific row, or creates a new one, if not found any.
Merge Merges the table with another DataTable.
NewRow Creates a new DataRow.
RejectChanges Rolls back all changes made since the last call to AcceptChanges.
Reset Resets the table to its original state.
Select Returns an array of DataRow objects.

The DataRow Class

DataRow對象表示表中的行。它具有以下重要特性：

Properties Description
HasErrors Indicates if there are any errors.
Items Gets or sets the data stored in a specific column.
ItemArrays Gets or sets all the values for the row.
Table Returns the parent table.

下表顯示了DataRow類的一些重要方法：

Methods Description
AcceptChanges Accepts all changes made since this method was called.
BeginEdit Begins edit operation.
CancelEdit Cancels edit operation.
Delete Deletes the DataRow.
EndEdit Ends the edit operation.
GetChildRows Gets the child rows of this row.
GetParentRow Gets the parent row.
GetParentRows Gets parent rows of DataRow object.
RejectChanges Rolls back all changes made since the last call to AcceptChanges.

The DataAdapter Object

DataAdapter對象充當數據集對象和資料庫之間的中介。這有助於數據集包含來自多個資料庫或其他數據源的數據。

The DataReader Object

DataReader對象是DataSet和DataAdapter組合的替代對象。此對象提供對資料庫中數據記錄的面向連接的訪問。這些對象適合只讀訪問，例如填充列表，然後斷開連接。

DbCommand and DbConnection Objects

DbConnection對象表示到數據源的連接。可以在不同的命令對象之間共享連接。

DbCommand對象表示從檢索或操作數據發送到資料庫的命令或存儲過程。

Example

到目前爲止，我們已經使用了計算機中已經存在的表和資料庫。在本例中，我們將創建一個表，向其中添加列、行和數據，並使用GridView對象顯示該表。

源文件代碼如下所示：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="createdatabase._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
      
         <div>
            <asp:GridView ID="GridView1" runat="server">
            </asp:GridView>
         </div>
         
      </form>
   </body>
   
</html>

代碼隱藏文件如下所示：

namespace createdatabase
{
   public partial class _Default : System.Web.UI.Page
   {
      protected void Page_Load(object sender, EventArgs e)
      {
         if (!IsPostBack)
         {
            DataSet ds = CreateDataSet();
            GridView1.DataSource = ds.Tables["Student"];
            GridView1.DataBind();
         }
      }
      
      private DataSet CreateDataSet()
      {
         //creating a DataSet object for tables
         DataSet dataset = new DataSet();

         // creating the student table
         DataTable Students = CreateStudentTable();
         dataset.Tables.Add(Students);
         return dataset;
      }
      
      private DataTable CreateStudentTable()
      {
         DataTable Students = new DataTable("Student");

         // adding columns
         AddNewColumn(Students, "System.Int32", "StudentID");
         AddNewColumn(Students, "System.String", "StudentName");
         AddNewColumn(Students, "System.String", "StudentCity");

         // adding rows
         AddNewRow(Students, 1, "M H Kabir", "Kolkata");
         AddNewRow(Students, 1, "Shreya Sharma", "Delhi");
         AddNewRow(Students, 1, "Rini Mukherjee", "Hyderabad");
         AddNewRow(Students, 1, "Sunil Dubey", "Bikaner");
         AddNewRow(Students, 1, "Rajat Mishra", "Patna");

         return Students;
      }

      private void AddNewColumn(DataTable table, string columnType, string  columnName)
      {
         DataColumn column = table.Columns.Add(columnName,  Type.GetType(columnType));
      }

      //adding data into the table
      private void AddNewRow(DataTable table, int id, string name, string city)
      {
         DataRow newrow = table.NewRow();
         newrow["StudentID"] = id;
         newrow["StudentName"] = name;
         newrow["StudentCity"] = city;
         table.Rows.Add(newrow);
      }
   }
}

執行程序時，請注意以下事項：

  • 應用程式首先創建一個數據集，並使用grid view控制項的DataBind（）方法將其與GridView控制項綁定。

  • Createdataset（）方法是一個用戶定義的函數，它創建一個新的數據集對象，然後調用另一個用戶定義的方法CreateStudentTable（）來創建表並將其添加到數據集的表集合中。

  • CreateStudentTable（）方法調用用戶定義的方法AddNewColumn（）和AddNewRow（）來創建表的列和行，並向行中添加數據。

執行頁面時，它返回表中的行，如下所示：