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

 

 

转载于:https://www.cnblogs.com/csl-office-vb-sql-net/archive/2010/02/11/1667562.html