System.drawing.graphics的内存不足异常错误

Question

我有一个vb.net应用程序，它使用system.drawing在combobox下拉列表中显示多个数据字段。但是每次打开它时它都会崩溃并获取错误消息未处理的异常（内存不足）

  

System.OutOfMemoryException：内存不足。在   System.Drawing.Graphics.FromHdcInternal（IntPtr hdc）at   System.Windows.Forms.ComboBox.WmReflectDrawItem（Message＆amp; m）at at   System.Windows.Forms.ComboBox.WndProc（Message＆amp; m）at   System.Windows.Forms.Control.ControlNativeWindow.OnMessage（Message＆amp; m）   在System.Windows.Forms.Control.ControlNativeWindow.WndProc（Message＆amp;   m）在System.Windows.Forms.NativeWindow.Callback（IntPtr hWnd，Int32）   msg，IntPtr wparam，IntPtr lparam）

为下拉列表绘制代码

Private Sub NamesComboBox_DrawItem2(sender As Object, g As System.Windows.Forms.DrawItemEventArgs) Handles Grower.DrawItem

        Grower.DrawMode = DrawMode.OwnerDrawVariable
        Grower.Size = New System.Drawing.Size(75, 120)
        Grower.DropDownStyle = ComboBoxStyle.DropDown
        Grower.DropDownWidth = 500
        g.DrawBackground()

        Dim drv As DataRowView = CType(Grower.Items(g.Index), DataRowView)

        ' Retrieve the value of each column.
        Dim Grow As String = drv("Grower").ToString()
        Dim Ptype As String = drv("Poultry Type").ToString()
        Dim GrowName As String = drv("Grower Name").ToString()
        Dim BoardAccount As String = drv("Board Account").ToString()
        Dim ChickAccount As String = drv("Chick Account").ToString()
        Dim CatchingAccount As String = drv("Catching Account").ToString()


        ' Get the bounds for the first column
        Dim a1 As Rectangle = g.Bounds
        a1.Width = 50


        ' Draw the text on the first column
        Using sb As SolidBrush = New SolidBrush(g.ForeColor)
            g.Graphics.DrawString(Grow, g.Font, sb, a1)
        End Using

        ' Draw a line to isolate the columns 
        Using p As Pen = New Pen(Color.Black)
            g.Graphics.DrawLine(p, a1.Right, 0, a1.Right, a1.Bottom)
        End Using



        ' Get the bounds for the second column
        Dim a2 As Rectangle = g.Bounds
        a2.X = a1.Width + 1
        a2.Width = 15

        ' Draw the text on the second column
        Using sb As SolidBrush = New SolidBrush(g.ForeColor)
            g.Graphics.DrawString(Ptype, g.Font, sb, a2)
        End Using

        Using p As Pen = New Pen(Color.Black)
            g.Graphics.DrawLine(p, a2.Right, 0, a2.Right, a2.Bottom)
        End Using

        ' Get the bounds for the third column
        Dim a3 As Rectangle = g.Bounds
        a3.X = 65
        a3.Width = 180

        ' Draw the text on the third column
        Using sb As SolidBrush = New SolidBrush(g.ForeColor)
            g.Graphics.DrawString(GrowName, g.Font, sb, a3)
        End Using


        Using p As Pen = New Pen(Color.Black)
            g.Graphics.DrawLine(p, a3.Right, 0, a3.Right, a3.Bottom)
        End Using

        ' Get the bounds for the third column
        Dim a4 As Rectangle = g.Bounds
        a4.X = 245
        a4.Width = 50

        ' Draw the text on the third column
        Using sb As SolidBrush = New SolidBrush(g.ForeColor)
            g.Graphics.DrawString(BoardAccount, g.Font, sb, a4)
        End Using

        Using p As Pen = New Pen(Color.Black)
            g.Graphics.DrawLine(p, a4.Right, 0, a4.Right, a4.Bottom)
        End Using

        ' Get the bounds for the third column
        Dim a5 As Rectangle = g.Bounds
        a5.X = 295
        a5.Width = 50

        ' Draw the text on the third column
        Using sb As SolidBrush = New SolidBrush(g.ForeColor)
            g.Graphics.DrawString(ChickAccount, g.Font, sb, a5)
        End Using


        Using p As Pen = New Pen(Color.Black)
            g.Graphics.DrawLine(p, a5.Right, 0, a5.Right, a5.Bottom)
        End Using

        ' Get the bounds for the third column
        Dim a6 As Rectangle = g.Bounds
        a6.X = 345
        a6.Width = 50

        ' Draw the text on the third column
        Using sb As SolidBrush = New SolidBrush(g.ForeColor)
            g.Graphics.DrawString(CatchingAccount, g.Font, sb, a6)
        End Using


    End Sub

Answer 1

paint方法不应该更改任何控件的属性，所以将这些行移动到窗体的构造函数或OnLoad覆盖：

Grower.DrawMode = DrawMode.OwnerDrawVariable
Grower.Size = New System.Drawing.Size(75, 120)
Grower.DropDownStyle = ComboBoxStyle.DropDown
Grower.DropDownWidth = 500

如果需要OwnerDrawVariable，您的代码中并不清楚。尝试使用OwnerDrawFixed并根据自己的喜好设置ItemHeight属性。此外，ComboBox没有可调高度，因此您只能设置宽度。