无法通过自定义方法更改按钮的背景颜色

Question

这是我的代码，可以更改任何按钮的背景颜色，但它不起作用，我也不知道出了什么问题：

Public Sub color(ByVal backcolor As System.Drawing.Color)
    backcolor = Drawing.Color.CadetBlue
End Sub

这是我在单击按钮时调用它的方式。它应该改变 Button1 的背景颜色，但它没有。我做得对还是我漏掉了什么？

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    color(Button1.BackColor)
End Sub

Answer 1

System.Drawing.Color是一个值类型（结构）。当您将它传递给 color 方法时，只会传递一个副本，而您的方法只会更改该副本。您应该将 Sub 更改为函数和 return 颜色并将其分配给按钮的 BackColor 属性:

Public Function color() As System.Drawing.Color
    Return System.Drawing.Color.CadetBlue
End Function

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    Button1.BackColor = color()
End Sub

尽管该功能没有增加任何价值。您可能应该直接设置颜色：

Button1.BackColor = System.Drawing.Color.CadetBlue

根据@VisualVincent 的评论，您可以在您的 Sub:

中使用 ByRef

Private Sub ChangeColor(ByRef c As System.Drawing.Color)
    c = Color.CadetBlue
End Sub

Answer 2

Public Sub color(ByVal btn As Control, ByVal clr As System.Drawing.Color)
    btn.BackColor = clr
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    color(Button1, Drawing.Color.CadetBlue)
End Sub

或者

Public Sub color(ByVal btn As Control)
    btn.BackColor = Drawing.Color.CadetBlue
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    color(Button1)
End Sub

适用于任何控件（文本框、标签 e.t.c）

Answer 3

您可以创建一个扩展方法来执行此操作。创建一个public模块如下：

Public Module Module1    
    <Runtime.CompilerServices.Extension()>
    Public Sub SetBackColourToCadetBlue(aButton As Button)
    'Use the following line for Telerik Button
    'Public Sub SetBackColourToCadetBlue(aButton As Telerik.WinControls.UI.RadButton) 
        aButton.BackColor = Color.CadetBlue
    End Sub
End Module

您可以调用以下命令来设置任何按钮的背景颜色：

Button1.SetBackColourToCadetBlue()

无法通过自定义方法更改按钮的背景颜色

Cannot change the back color of a button via a custom method

.net

vb.net

colors

backcolor

subroutine