窗体水印C#转VB.Net

Question

麻烦各位帮忙把以下C#源码转为VB.Net源码

public static class ControlExtension
{
    const float cos30 = 0.866f;
    const float sin30 = 0.5f;
    public static void BindWaterMark(this Control ctrl)
    {
        if (ctrl == null || ctrl.IsDisposed)
            return;
        // 绘制水印
        if (ctrl.HaveEventHandler("Paint", "BindWaterMark"))
            return;
        ctrl.Paint += (sender, e) =>
        {
            System.Windows.Forms.Control paintCtrl = sender as System.Windows.Forms.Control;
            var g = e.Graphics;
            g.SmoothingMode = SmoothingMode.AntiAlias;
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;

            // 计算控件位置
            int offsetX = 0;
            int offsetY = 0;
            while (paintCtrl.Parent != null)
            {
                offsetX += paintCtrl.Location.X;
                offsetY += paintCtrl.Location.Y;
                paintCtrl = paintCtrl.Parent;
            }

            // 平移画布到窗体左上角
            g.TranslateTransform(0 - offsetX, 0 - offsetY + 32);

            //逆时针旋转30度
            g.RotateTransform(-30);

            for (int x = 0; x < e.ClipRectangle.Right + 64 + offsetX; x += 128)
            {
                for (int y = 0; y < e.ClipRectangle.Bottom + 64 + offsetY; y += 128)
                {
                    // 计算文字起点位置
                    float x1 = cos30 * x - sin30 * y;
                    float y1 = sin30 * x + cos30 * y;

                    //画上文字
                    g.DrawString("水印文字" , new Font("微软雅黑", 16, FontStyle.Regular  ),
                        new SolidBrush(Color.FromArgb(50, 100, 100, 100)), x1, y1);   
                }
            }
        };
        // 子控件绑定绘制事件
        foreach (System.Windows.Forms.Control child in ctrl.Controls)
            BindWaterMark(child);
    }

    public static bool HaveEventHandler(this Control control, string eventName, string methodName)
    {
        //获取Control类定义的所有事件的信息
        PropertyInfo pi = (control.GetType()).GetProperty("Events", BindingFlags.Instance | BindingFlags.NonPublic);
        //获取Control对象control的事件处理程序列表
        EventHandlerList ehl = (EventHandlerList)pi.GetValue(control, null);

        //获取Control类 eventName 事件的字段信息
        FieldInfo fieldInfo = (typeof(Control)).GetField(string.Format("Event{0}", eventName), BindingFlags.Static | BindingFlags.NonPublic);
        //用获取的 eventName 事件的字段信息，去匹配 control 对象的事件处理程序列表，获取control对象 eventName 事件的委托对象
        //事件使用委托定义的，C#中的委托时多播委托，可以绑定多个事件处理程序，当事件发生时，这些事件处理程序被依次执行
        //因此Delegate对象，有一个GetInvocationList方法，用来获取这个委托已经绑定的所有事件处理程序
        Delegate d = ehl[fieldInfo.GetValue(null)];

        if (d == null)
            return false;

        foreach (Delegate del in d.GetInvocationList())
        {
            string anonymous = string.Format("<{0}>", methodName);
            //判断一下某个事件处理程序是否已经被绑定到 eventName 事件上
            if (del.Method.Name == methodName || del.Method.Name.StartsWith(anonymous))
            {
                return true;
            }
        }

        return false;
    }
}

Answer 1

Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Reflection
Imports System.Windows.Forms

Public Module ControlExtension
    Private Const cos30 As Single = 0.866F
    Private Const sin30 As Single = 0.5F

    <System.Runtime.CompilerServices.Extension>
    Public Sub BindWaterMark(ctrl As Control)
        If ctrl Is Nothing OrElse ctrl.IsDisposed Then
            Return
        End If

        ' 绘制水印
        If ctrl.HaveEventHandler("Paint", "BindWaterMark") Then
            Return
        End If

        AddHandler ctrl.Paint, Sub(sender, e)
                                   Dim paintCtrl As System.Windows.Forms.Control = TryCast(sender, System.Windows.Forms.Control)
                                   Dim g = e.Graphics
                                   g.SmoothingMode = SmoothingMode.AntiAlias
                                   g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias

                                   ' 计算控件位置
                                   Dim offsetX As Integer = 0
                                   Dim offsetY As Integer = 0
                                   While paintCtrl.Parent IsNot Nothing
                                       offsetX += paintCtrl.Location.X
                                       offsetY += paintCtrl.Location.Y
                                       paintCtrl = paintCtrl.Parent
                                   End While

                                   ' 平移画布到窗体左上角
                                   g.TranslateTransform(0 - offsetX, 0 - offsetY + 32)

                                   '逆时针旋转30度
                                   g.RotateTransform(-30)

                                   For x As Integer = 0 To e.ClipRectangle.Right + 64 + offsetX Step 128
                                       For y As Integer = 0 To e.ClipRectangle.Bottom + 64 + offsetY Step 128
                                           ' 计算文字起点位置
                                           Dim x1 As Single = cos30 * x - sin30 * y
                                           Dim y1 As Single = sin30 * x + cos30 * y

                                           '画上文字
                                           g.DrawString("水印文字", New Font("微软雅黑", 16, FontStyle.Regular),
                                                        New SolidBrush(Color.FromArgb(50, 100, 100, 100)), x1, y1)
                                       Next
                                   Next
                               End Sub

        ' 子控件绑定绘制事件
        For Each child As System.Windows.Forms.Control In ctrl.Controls
            BindWaterMark(child)
        Next
    End Sub

    <System.Runtime.CompilerServices.Extension>
    Public Function HaveEventHandler(control As Control, eventName As String, methodName As String) As Boolean
        '获取Control类定义的所有事件的信息
        Dim pi As PropertyInfo = control.GetType().GetProperty("Events", BindingFlags.Instance Or BindingFlags.NonPublic)
        '获取Control对象control的事件处理程序列表
        Dim ehl As EventHandlerList = DirectCast(pi.GetValue(control, Nothing), EventHandlerList)

        '获取Control类 eventName 事件的字段信息
        Dim fieldInfo As FieldInfo = GetType(Control).GetField($"Event{eventName}", BindingFlags.Static Or BindingFlags.NonPublic)
        '用获取的 eventName 事件的字段信息，去匹配 control 对象的事件处理程序列表，获取control对象 eventName 事件的委托对象
        '事件使用委托定义的，C#中的委托时多播委托，可以绑定多个事件处理程序，当事件发生时，这些事件处理程序被依次执行
        '因此Delegate对象，有一个GetInvocationList方法，用来获取这个委托已经绑定的所有事件处理程序
        Dim d As [Delegate] = ehl(fieldInfo.GetValue(Nothing))

        If d Is Nothing Then
            Return False
        End If

        For Each del As [Delegate] In d.GetInvocationList()
            Dim anonymous As String = $"<{methodName}>"
            '判断一下某个事件处理程序是否已经被绑定到 eventName 事件上
            If del.Method.Name = methodName OrElse del.Method.Name.StartsWith(anonymous) Then
                Return True
            End If
        Next

        Return False
    End Function
End Module