7 使用DataGridView控件

7.1.6 处理单元格事件 

 

代码

   
     

    
      
    
       
    
      Sub
    
       DataGridView1_CellValidating(
    
      ByVal
    
       sender 
    
      As
    
       
    
      Object
    
      ,
 
    
      ByVal
    
       e 
    
      As
    
       System.Windows.Forms.DataGridViewCellValidatingEventArgs
 ) 
    
      Handles
    
       DataGridView1.CellValidating
 Debug.WriteLine(
    
      "
    
      Cell Validating: 
    
      "
    
       
    
      &
    
       e.RowIndex 
    
      &
    
       
    
      "
    
      , 
    
      "
    
       
    
      &
    
       e.ColumnIndex)
 
    
      If
    
       e.ColumnIndex 
    
      =
    
       
    
      1
    
       
    
      AndAlso
    
      
 e.FormattedValue.ToString.Trim.Length 
    
      =
    
       
    
      0
    
       
    
      Then
    
      
 e.Cancel 
    
      =
    
       
    
      True
    
      
 
    
      End
    
       
    
      If
    
      
 
    
      End Sub
    
      

   
     

 

 

  

7.1.7.5 使用DataGridViewImageColumn对象

 

 用上下文菜单向ImageCell中插入图像 

代码

     Dim  currentPhotoCell  As  DataGridViewImageCell
     Sub  InsertPhotoFromFileToolStripMenuItem_Click( ByVal  sender  As   Object , _
                                                    ByVal  e  As  EventArgs _
                                                   )  Handles  InsertPhotoFromFileToolStripMenuItem.Click
         Dim  dlg  As   New  OpenFileDialog
        dlg.Multiselect  =   False
        dlg.Filter  =   " GIF|*.gif|BMP|*.bmp|JPEG|*.jpg;*.jpeg|All Files|*.* "
        dlg.FilterIndex  =   3
        dlg.Title  =   " select a photo to insert "
         If  dlg.ShowDialog  <>  Windows.Forms.DialogResult.OK  Then   Return
         Dim  bmp  As   New  Bitmap(dlg.FileName)
        currentPhotoCell.Value  =  bmp
     End Sub

  

为上下文菜单设置CurrentPhotoCell变量值

代码

     Sub  EmployeesDataGridView_CellContextMenuStripNeeded( ByVal  sender  As   Object , _
                                                          ByVal  e  As  DataGridViewCellContextMenuStripNeededEventArgs _
                                                         )  Handles  EmployeesDataGridView.CellContextMenuStripNeeded
         Dim  dg  As  DataGridView  =   CType (sender, DataGridView)
         If   TypeOf  dg.Columns(e.ColumnIndex)  Is  DataGridViewImageColumn  Then
            currentPhotoCell  =   CType (dg.Rows(e.RowIndex).Cells(e.ColumnIndex), DataGridViewImageCell)
         End   If
     End Sub

  

 将DataGridViewImageCell对象中的图像保存到文件中 

代码

Imports  System.IO
Imports  System.Drawing.Imaging

     Private   Sub  SavePhotoToFileToolStripMenuItem_Click( ByVal  sender  As  System.Object, _
                                                        ByVal  e  As  System.EventArgs _
                                                       )  Handles  SavePhotoToFileToolStripMenuItem.Click
         Const  oleOffset  As   Integer   =   78
         Const  oleTypeStart  As   Integer   =   20
         Const  oleTypeLength  As   Integer   =   12

         Dim  imageBytes  As   Byte ()  =   CType (currentPhotoCell.Value,  Byte ())

         If  imageBytes  Is   Nothing   Or  imageBytes.Length  =   0   Then   Return

         Dim  dlg  As   New  SaveFileDialog
        dlg.AddExtension  =   True
        dlg.Filter  =   " GIF|*.gif|BMP|*.bmp|JPEG|*.jpg;*.jpeg|All Files|*.* "
        dlg.FilterIndex  =   2
        dlg.Title  =   " Enter a file name for this photo "
        dlg.FileName  =   " EmployeePhoto.bmp "

         If  dlg.ShowDialog  <>  Windows.Forms.DialogResult.OK  Then   Return

         Dim  tempStream  As  MemoryStream
         Dim  type  As   String   =  System.Text.Encoding.ASCII.GetString(imageBytes, oleTypeStart, oleTypeLength)
         If  type  =   " Bitmap Image "   Then
            tempStream  =   New  MemoryStream(imageBytes, oleOffset, imageBytes.Length  -  oleOffset)
         Else
            tempStream  =   New  MemoryStream(imageBytes,  0 , imageBytes.Length)
         End   If

         Dim  bmp  As   New  Bitmap(tempStream)
        bmp.Save(dlg.FileName, ParseImageFormat(dlg.FileName))
     End Sub

     Function  ParseImageFormat( ByVal  filename  As   String )  As  ImageFormat
         Dim  ext  As   String   =  Path.GetExtension(filename).ToLower
         Select   Case  ext
             Case   " bmp "
                 Return  ImageFormat.Bmp
             Case   " jpg " ,  " jpeg "
                 Return  ImageFormat.Jpeg
             Case   " gif "
                 Return  ImageFormat.Gif
             Case   Else
                 Return  ImageFormat.Bmp
         End   Select
         Return   Nothing
     End Function

 

 7.1.9 实现Virtual模式

类Fruit的代码

代码

Public   Class  Fruit
     Public   Property  Name()  As   String
         Get
             Return  _name
         End   Get
         Set ( ByVal  value  As   String )
            _name  =  value
         End   Set
     End Property
     Dim  _name  As   String

     Public   Property  Calories()  As   Decimal
         Get
             Return  _calories
         End   Get
         Set ( ByVal  value  As   Decimal )
            _calories  =  value
         End   Set
     End Property
     Dim  _calories  As   Decimal

     Public   Property  Carbs()  As   Decimal
         Get
             Return  _carbs
         End   Get
         Set ( ByVal  value  As   Decimal )
            _carbs  =  value
         End   Set
     End Property
     Dim  _carbs  As   Decimal

     Public   Sub   New ( ByVal  name  As   String ,  ByVal  calories  As   Decimal ,  ByVal  carbs  As   Decimal )
         Me .Name  =  name
         Me .Calories  =  calories
         Me .Carbs  =  carbs
     End Sub
End Class

 

实现Virtual模式 

代码

Public   Class  Form1
     Private  fruitList  As   New  List( Of  Fruit)
     Private  rowInEdit  As   Integer   =   - 1
     Private  fruitInEdit  As  Fruit  =   Nothing

     Sub  Form1_Load( ByVal  sender  As  System.Object,  ByVal  e  As  System.EventArgs)  Handles   MyBase .Load
         With  fruitList
            .Add( New  Fruit( " Apple " ,  44 ,  10.5 ))
            .Add( New  Fruit( " Banana " ,  107 ,  26 ))
            .Add( New  Fruit( " Orange " ,  35 ,  8.5 ))
         End   With
        DataGridView1.RowCount  =  fruitList.Count  +   1

     End Sub

     Sub  DataGridView1_CellValueNeeded( ByVal  sender  As   Object ,  ByVal  e  As  DataGridViewCellValueEventArgs)  Handles  DataGridView1.CellValueNeeded
         If  e.RowIndex  =  DataGridView1.RowCount  -   1   Then
             Return
         End   If

         Dim  tmpFruit  As  Fruit  =   Nothing
         If  e.RowIndex  =  rowInEdit  Then
            tmpFruit  =   Me .fruitInEdit
         Else
            tmpFruit  =  fruitList(e.RowIndex)
         End   If

         Select   Case   Me .DataGridView1.Columns(e.ColumnIndex).Name
             Case   " FruitName "
                e.Value  =  tmpFruit.Name
             Case   " Calories "
                e.Value  =  tmpFruit.Calories
             Case   " Carbs "
                e.Value  =  tmpFruit.Carbs
         End   Select
     End Sub
End Class

 

向DataGridView对象添加新行 

代码

     Sub  DataGridView1_NewRowNeeded( ByVal  sender  As   Object ,  ByVal  e  As  DataGridViewRowEventArgs)  Handles  DataGridView1.NewRowNeeded
        fruitInEdit  =   New  Fruit( "" ,  0 ,  0 )
        rowInEdit  =  DataGridView1.Rows.Count  -   1
     End Sub

     Sub  DataGridView1_CellValuePushed( ByVal  sender  As   Object ,  ByVal  e  As  DataGridViewCellValueEventArgs)  Handles  DataGridView1.CellValuePushed
         Dim  tmpFruit  As  Fruit  =   Nothing
         If  e.RowIndex  <  fruitList.Count  Then
             If  fruitInEdit  Is   Nothing   Then
                 With  fruitList(e.RowIndex)
                    fruitInEdit  =   New  Fruit(.Name, .Calories, .Carbs)
                 End   With
             End   If

            tmpFruit  =  fruitInEdit
            rowInEdit  =  e.RowIndex
         Else
            tmpFruit  =  fruitInEdit
         End   If

         Dim  newValue  As   String   =  TryCast(e.Value,  String )
         Select   Case  DataGridView1.Columns(e.ColumnIndex).Name
             Case   " FruitName "
                tmpFruit.Name  =  newValue
             Case   " Calories "
                tmpFruit.Calories  =   Decimal .Parse(newValue)
             Case   " Carbs "
                tmpFruit.Carbs  =   Decimal .Parse(newValue)
         End   Select
     End Sub

     Sub  DataGridView1_RowValidated( ByVal  sender  As   Object ,  ByVal  e  As  DataGridViewCellEventArgs)  Handles  DataGridView1.RowValidated
         If  e.RowIndex  >=  fruitList.Count  And  e.RowIndex  <>  DataGridView1.Rows.Count  -   1   Then
            fruitList.Add(fruitInEdit)
            fruitInEdit  =   Nothing
            rowInEdit  =   - 1
         ElseIf   Not  fruitInEdit  Is   Nothing   And  e.RowIndex  <  fruitList.Count  Then
            fruitList(e.RowIndex)  =  fruitInEdit
            fruitInEdit  =   Nothing
            rowInEdit  =   - 1
         Else
            fruitInEdit  =   Nothing
            rowInEdit  =   - 1
         End   If
     End Sub

  

添加删除行和取消取行编辑的功能

代码

     Sub  DataGridView1_UserDeletingRow( ByVal  sender  As   Object ,  ByVal  e  As  DataGridViewRowCancelEventArgs)  Handles  DataGridView1.UserDeletingRow
         If  e.Row.Index  <  fruitList.Count  Then
            fruitList.RemoveAt(e.Row.Index)
         End   If

         If  e.Row.Index  =   Me .rowInEdit  Then
            rowInEdit  =   - 1
            fruitInEdit  =   Nothing
         End   If
     End Sub

     Sub  DataGridView1_CancelRowEdit( ByVal  sender  As   Object ,  ByVal  e  As  QuestionEventArgs)  Handles  DataGridView1.CancelRowEdit
         If  rowInEdit  =  DataGridView1.Rows.Count  -   2   And  rowInEdit  =  fruitList.Count  Then
            fruitInEdit  =   New  Fruit( "" ,  0 ,  0 )
         Else
            fruitInEdit  =   Nothing
            rowInEdit  =   - 1
         End   If
     End Sub