vb.net 如何从另一种形式调用公共函数
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How to call a public function from another form
提问by Caesium95
Frm1contains the code for validation of textbox:
Frm1包含用于验证的代码textbox：
Public Function AlphabeticalOnly(ByVal Str As String) As Boolean
Dim pattern As String = "^[a-zA-Z\s]+$"
Dim reg As New Regex(pattern)
If reg.IsMatch(Str) = False Then
MsgBox(Str & " is invalid! Please enter alphabetical characters only!", MsgBoxStyle.Critical, "Error")
End If
Return reg.IsMatch(Str)
End Function
Because there're quite an amount of validations, I don't want to repeat all the code again in the other forms.
因为有相当多的验证，我不想在其他表单中再次重复所有代码。
Private Sub btnDone_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDone.Click
If AlphabeticalOnly(txtName.Text) = False Then
Exit Sub
End If
...
End Sub
I tried the code above in another form, but the error list shows that AlphabeticalOnlyis not declared.
我以另一种形式尝试了上面的代码，但错误列表显示AlphabeticalOnly未声明。
Is there anything that I need to add to my code?
有什么我需要添加到我的代码中的吗？
回答by David
First of all, don't put the function on a form. If it's common code shared by all forms, put it in its own class file.
首先，不要把函数放在一个表单上。如果它是所有表单共享的公共代码，请将其放在自己的类文件中。
Second, this common code shouldn't be prompting the user with a message box. This function shouldjust perform the logic and nothing more. (This also makes the function easier to unit test.) Then allow the consuming code (in this case a form) to interact with the user. (Especially since the current implementation checks the match twice, which isn't necessary.)
其次，这个通用代码不应该用消息框提示用户。这个函数应该只执行逻辑，仅此而已。（这也使函数更易于单元测试。）然后允许使用代码（在本例中为表单）与用户交互。（特别是因为当前的实现检查匹配两次，这是没有必要的。）
Since this function doesn't rely on object state, you can make it Shared. Something like this:
由于此函数不依赖于对象状态，因此您可以将其设为Shared. 像这样的东西：
Public Class CommonFunctions
Public Shared Function IsAlphabeticalOnly(ByVal Str As String) As Boolean
Dim pattern As String = "^[a-zA-Z\s]+$"
Dim reg As New Regex(pattern)
Return reg.IsMatch(Str)
End Function
End Class
Then on your forms you can invoke that function:
然后在您的表单上，您可以调用该函数：
If CommonFunctions.IsAlphabeticalOnly(txtName.Text) = False Then
MsgBox(Str & " is invalid! Please enter alphabetical characters only!", MsgBoxStyle.Critical, "Error")
End If
