Henry手记：WinForm Datagrid结构剖析（三）类代码

-------------------X类的代码X---------------------
Option Strict On
Option Explicit On
Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Data

Public Class DataGridComboBox
‘与DataGridTextBox类相类似地定义一个在下拉框列类中使用的ComboBox
Inherits ComboBox
Public Sub New()
MyBase.New()
End Sub
Public isInEditOrNavigateMode As Boolean = True
End Class

Public Class DataGridComboBoxColumn
Inherits DataGridColumnStyle
' 与用户界面相关的变量
Private xMargin As Integer = 2
Private yMargin As Integer = 1
Private Combo As DataGridComboBox
Private _DisplayMember As String
Private _ValueMember As String
' 用于跟踪编辑状态变化的变量
Private OldVal As String = String.Empty
Private InEdit As Boolean = False
'构造函数 – 实例的DisplayMember, ValueMember值为由父类传来的integer类型的值
Public Sub New(ByRef DataSource As DataTable, _
ByVal DisplayMember As Integer, _
ByVal ValueMember As Integer)
Combo = New DataGridComboBox()
_DisplayMember = DataSource.Columns.Item(index:=DisplayMember).ToString
_ValueMember = DataSource.Columns.Item(index:=ValueMember).ToString
With Combo
.Visible = False
.DataSource = DataSource
.DisplayMember = _DisplayMember
.ValueMember = _ValueMember
End With
End Sub
'构造函数– 实例的DisplayMember, ValueMember 是String类型的值
Public Sub New(ByRef DataSource As DataTable, _
ByVal DisplayMember As String, _
ByVal ValueMember As String)
Combo = New DataGridComboBox()
With Combo
.Visible = False
.DataSource = DataSource
.DisplayMember = DisplayMember
.ValueMember = ValueMember
End With
End Sub
'------------------------------------------------------
'从 DataGridColumnStyle类继承下来的方法
'------------------------------------------------------
' 焦点离开combobox格后的改变
Protected Overloads Overrides Sub Abort(ByVal RowNum As Integer)
Debug.WriteLine("Abort()")
RollBack()
HideComboBox()
EndEdit()
End Sub
' 接受改变
Protected Overloads Overrides Function Commit(ByVal DataSource As CurrencyManager, _
ByVal RowNum As Integer) As Boolean
HideComboBox()
If Not InEdit Then
Return True
End If
Try
Dim Value As Object = Combo.SelectedValue
If NullText.Equals(Value) Then
Value = Convert.DBNull
End If
SetColumnValueAtRow(DataSource, RowNum, Value)
Catch e As Exception
RollBack()
Return False
End Try
EndEdit()
Return True
End Function
' 移开聚焦
Protected Overloads Overrides Sub ConcedeFocus()
Combo.Visible = False
End Sub
' 编辑单元格
Protected Overloads Overrides Sub Edit(ByVal Source As CurrencyManager, _
ByVal Rownum As Integer, _
ByVal Bounds As Rectangle, _
ByVal [ReadOnly] As Boolean, _
ByVal InstantText As String, _
ByVal CellIsVisible As Boolean)
Combo.Text = String.Empty
Dim OriginalBounds As Rectangle = Bounds
OldVal = Combo.Text
If CellIsVisible Then
Bounds.Offset(xMargin, yMargin)
Bounds.Width -= xMargin * 2
Bounds.Height -= yMargin
Combo.Bounds = Bounds
Combo.Visible = True
Else
Combo.Bounds = OriginalBounds
Combo.Visible = False
End If
Combo.SelectedValue = GetText(GetColumnValueAtRow(Source, Rownum))
If Not InstantText Is Nothing Then
Combo.SelectedValue = InstantText
End If
Combo.RightToLeft = Me.DataGridTableStyle.DataGrid.RightToLeft
Combo.Focus()
If InstantText Is Nothing Then
Combo.SelectAll()
Else
Dim [End] As Integer = Combo.Text.Length
Combo.Select([End], 0)
End If
If Combo.Visible Then
DataGridTableStyle.DataGrid.Invalidate(OriginalBounds)
End If
InEdit = True
End Sub
Protected Overloads Overrides Function GetMinimumHeight() As Integer
' 设置combobox的最小高度
Return Combo.PreferredHeight + yMargin
End Function
Protected Overloads Overrides Function GetPreferredHeight(ByVal g As Graphics, _
ByVal Value As Object) As Integer
Debug.WriteLine("GetPreferredHeight()")
Dim NewLineIndex As Integer = 0
Dim NewLines As Integer = 0
Dim ValueString As String = Me.GetText(Value)
Do
While NewLineIndex <> -1
NewLineIndex = ValueString.IndexOf("r/n", NewLineIndex + 1)
NewLines += 1
End While
Loop
Return FontHeight * NewLines + yMargin
End Function
Protected Overloads Overrides Function GetPreferredSize(ByVal g As Graphics, _
ByVal Value As Object) As Size
Dim Extents As Size = Size.Ceiling(g.MeasureString(GetText(Value), _
Me.DataGridTableStyle.DataGrid.Font))
Extents.Width += xMargin * 2 + DataGridTableGridLineWidth
Extents.Height += yMargin
Return Extents
End Function
Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager, _
ByVal RowNum As Integer)
Paint(g, Bounds, Source, RowNum, False)
End Sub
Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager, _
ByVal RowNum As Integer, _
ByVal AlignToRight As Boolean)
Dim Text As String = GetText(GetColumnValueAtRow(Source, RowNum))
PaintText(g, Bounds, Text, AlignToRight)
End Sub
Protected Overloads Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager, _
ByVal RowNum As Integer, _
ByVal BackBrush As Brush, _
ByVal ForeBrush As Brush, _
ByVal AlignToRight As Boolean)

Dim Text As String = GetText(GetColumnValueAtRow(Source, RowNum))
PaintText(g, Bounds, Text, BackBrush, ForeBrush, AlignToRight)
End Sub
Protected Overloads Overrides Sub SetDataGridInColumn(ByVal Value As DataGrid)
MyBase.SetDataGridInColumn(Value)
If Not (Combo.Parent Is Value) Then
If Not (Combo.Parent Is Nothing) Then
Combo.Parent.Controls.Remove(Combo)
End If
End If
If Not (Value Is Nothing) Then Value.Controls.Add(Combo)
End Sub
Protected Overloads Overrides Sub UpdateUI(ByVal Source As CurrencyManager, _
Val RowNum As Integer, ByVal InstantText As String)
Combo.Text = GetText(GetColumnValueAtRow(Source, RowNum))
If Not (InstantText Is Nothing) Then
Combo.Text = InstantText
End If
End Sub
－－－未完，见（三）使用代码一文－－－－－－－－－

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