如何把树与数据库的信息进行绑定

以前写了一个例子，演示如何通过数据库数据动态加载TreeNode，参看：

Http://blog.youkuaiyun.com/knight94/archive/2006/03/24/637699.aspx

 

可能原先的例子，只是显示如何动态加载一个树，没有考虑到后期的修改或删除之类的操作，因此我在原有基础上，扩展了更新操作。不过实现的基础，还是在程序中保存一个临时数据表，要注意的是，如果数据量比较大的话，考虑到效率以及资源使用等因素，则可以取消临时数据表，而直接去访问数据库即可，这可以根据实际应用来修改我的方法。

 

以下就具体说说实现的步骤。

首先，是创建临时数据表。

    private DataTable dtTree = null;

    private void CreateTable()

    {

        // Create data table

        dtTree = new DataTable( "TreeDBInfo" );

 

        // Add new data columns

        DataColumn dc = new DataColumn( "EmployeeID", typeof(int) );

        dtTree.Columns.Add( dc );

        // Set primary key column

        dtTree.PrimaryKey = new DataColumn[]{dc};

 

        dtTree.Columns.Add( new DataColumn( "EmployeeName", typeof(string) ) );

        dtTree.Columns.Add( new DataColumn( "Age", typeof(int) ) );

        dtTree.Columns.Add( new DataColumn( "Salary", typeof(double) ) );

        dtTree.Columns.Add( new DataColumn( "Address", typeof(string) ) );

        dtTree.Columns.Add( new DataColumn( "EmpParentID", typeof(int) ) );

 

        // Add records into table

        //'0' is that the type has no parent

        dtTree.Rows.Add( new object[]{1, "Parent1",30, 2000,"***", 0} );

        dtTree.Rows.Add( new object[]{2, "Parent2",30, 2000,"***", 0} );

        dtTree.Rows.Add( new object[]{3, "Parent3",32, 2000,"***", 0} );

 

        dtTree.Rows.Add( new object[]{4, "Child1",25, 1400,"***", 1} );

        dtTree.Rows.Add( new object[]{5, "Child2",27, 1600,"***", 1} );

        dtTree.Rows.Add( new object[]{6, "Child3",27, 1600,"***", 2} );

 

        dtTree.Rows.Add( new object[]{7, "GrandChild1",23, 1200,"***", 4} );

        dtTree.Rows.Add( new object[]{8, "GrandChild2",23, 1200,"***", 4} );

        dtTree.Rows.Add( new object[]{9, "GrandChild3",22, 1200,"***", 5} );

    }

 

接着就是通过数据表来加载TreeNode。

    private void CreateTree()

    {

        DataRow[] drArray = dtTree.Select( "EmpParentID=0",

                            "EmpParentID ASC",

                            DataViewRowState.CurrentRows );

        if( drArray.Length == 0 ) return;

 

        TreeNode tnNew = null;

        foreach( DataRow dr in drArray )

        {

            tnNew = trvDBBinding.Nodes.Add( dr["EmployeeName"].ToString() );

            tnNew.Tag = dr["EmployeeID"].ToString();//Save "EmployeeID" in node's tag

            CreateTreeNode( ref tnNew );

        }

    }

 

    private void CreateTreeNode( ref TreeNode tnParent )

    {

        //Get children data info

        DataRow[] drArray = dtTree.Select(

            string.Format( "EmpParentID = {0}", tnParent.Tag ),

            "EmpParentID ASC",

            DataViewRowState.CurrentRows );

        if( drArray.Length == 0 ) return;

 

        TreeNode tnNew = null;

        foreach( DataRow dr in drArray )

        {

            tnNew = tnParent.Nodes.Add( dr["EmployeeName"].ToString() );

            tnNew.Tag = dr["EmployeeID"].ToString();//Save "EmployeeID" in node's tag

            CreateTreeNode( ref tnNew );

        }

    }

 

这里需要注意的是，要保存每条记录的主键到每个TreeNode的Tag属性中，即使动态从数据库查询也是一样的，这样能唯一标明记录，从而快速定位。

 

为了方便操作，我用弹出对话框的方法来查看或者修改TreeNode信息，那么对话框的代码大致如下：

    private DataTable dtTree = null;

    private TreeNode tnSelected = null;

 

    // frmViewNode constructor

    public frmViewNode( ref DataTable TreeTable, ref TreeNode SelectedNode )

    {

        //

        // Required for Windows Form Designer support

        //

        InitializeComponent();

 

        //

        // TODO: Add any constructor code after InitializeComponent call

        //

 

        dtTree = TreeTable;

        tnSelected = SelectedNode;

    }

 

    private void ShowNodeInfo()

    {

        // Find node info from data table

        DataRow[] drArray = dtTree.Select(

            string.Format( "EmployeeID = {0}", tnSelected.Tag ),

            "EmployeeID ASC",

            DataViewRowState.CurrentRows );

        if( drArray.Length == 0 ) return;

        else if( drArray.Length == 1 )

        {

            // Show tree node info

            txtName.Text = drArray[0]["EmployeeName"].ToString();

            txtAge.Text = drArray[0]["Age"].ToString();

            txtSalary.Text = drArray[0]["Salary"].ToString();

            txtAddress.Text = drArray[0]["Address"].ToString();

        }

    }

 

    private void frmViewNode_Load(object sender, System.EventArgs e)

    {

        ShowNodeInfo();

    }

 

    private void btnOK_Click(object sender, System.EventArgs e)

    {

        // Find node info from data table

        DataRow[] drArray = dtTree.Select(

            string.Format( "EmployeeID = {0}", tnSelected.Tag ),

            "EmployeeID ASC",

            DataViewRowState.CurrentRows );

        if( drArray.Length == 0 ) return;

        else if( drArray.Length == 1 )

        {

            // Update data to data table

            drArray[0].BeginEdit();

            drArray[0]["EmployeeName"] = txtName.Text;

            drArray[0]["Age"] = txtAge.Text;

            drArray[0]["Salary"] = txtSalary.Text;

            drArray[0]["Address"] = txtAddress.Text;

            drArray[0].EndEdit();

        }

 

        // Update tree node

        tnSelected.Text = txtName.Text;

        this.DialogResult = DialogResult.OK;

    }

 

则在显示TreeView的窗体中弹出以上窗体的代码如下：

    private TreeNode tnSelected = null;

    private void trvDBBinding_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)

    {

        if( e.Button == MouseButtons.Left )

        {

            tnSelected = trvDBBinding.GetNodeAt( e.X, e.Y );

        }

    }

 

    private void trvDBBinding_DoubleClick(object sender, System.EventArgs e)

    {

        if( tnSelected != null )

        {

            //Open window to view treenode info

            frmViewNode myViewNode = new frmViewNode( ref dtTree, ref tnSelected );

            if( myViewNode.ShowDialog() == DialogResult.OK )

            {

                //Update database using "dtTree"

 

                dtTree.AcceptChanges();//Update datatable

            }

        }

    }

 

    private void trvDBBinding_AfterSelect(object sender, System.Windows.Forms.TreeViewEventArgs e)

    {

        tnSelected = e.Node;

    }

 

要注意的是，如何去更新数据库，是在“DoubleClick”事件中去做还是在弹出窗体中去做。我个人推荐在弹出的窗体中去更新，因为效率比较高，不管是通过临时数据表还是动态从数据库进行加载。

 

如果使用临时数据表的话，因为在更新DataTable的时候，已经定位到具体记录了，那么只要用DataAdapter去执行Update方法即可（别忘了给DataAdapter设定UpdateCommand，否则数据库什么都不会更新）；如果使用动态数据表的话，只需要设置相应的DBCommand，来进行更新操作即可。