KeyPress字母和间距

Question

下面是我的代码，用于验证我的文本框。目前，我只在Letter上使用它，但是我不知道如何允许空格。

Private Sub txtFirstname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtFirstname.KeyPress
    If Char.IsLetter(e.KeyChar) = False And Char.IsControl(e.KeyChar) = False Then
        MessageBox.Show("Letters only.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        ' Stop invalid character appearing in field
        e.KeyChar = Nothing
    End If
End Sub

Answer 1

使用Char.IsWhiteSpace(e.KeyChar)方法

我还建议使用AndAlso而不是And运算符。

If Char.IsLetter(e.KeyChar) = False AndAlso Char.IsControl(e.KeyChar) = False Then

操作员AndAlso避免多余的检查，如果第一个条件为负，则退出。

编辑

当你高效地实现函数时，应该看起来像这样。您还应该将它放在一个私有子例程中，并在KeyPress处理程序子例程中调用它。以便在要验证输入的每个事件中重用代码

Private Sub txtFirstname_KeyPress(ByVal sender As Object, ByVal e As     System.Windows.Forms.KeyPressEventArgs) Handles txtFirstname.KeyPress
    ValidateInput(e)
End Sub

Private Sub ValidateInput(e As EventArgs)
If Char.IsWhiteSpace(e.KeyChar) = False Then        
    If Char.IsLetter(e.KeyChar) = False And Char.IsControl(e.KeyChar) = False Then
                MessageBox.Show("Letters only.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                ' Stop invalid character appearing in field
                e.KeyChar = Nothing
        End If
     End If
End Sub

Answer 2

您可以使用以下命令检查:字母、数字和空格(Tab、空格和enter)：

Private Sub textBox1_KeyPress(sender As Object, e As KeyPressEventArgs)
  e.Handled = True
  Dim IsLetter As Boolean = (e.KeyChar >= 65 AndAlso e.KeyChar <= 90) OrElse (e.KeyChar >= 97 AndAlso e.KeyChar <= 122)
  Dim IsNumber As Boolean = (e.KeyChar >= 48 AndAlso e.KeyChar <= 57)
  Dim IsWhiteSpace As Boolean = (e.KeyChar = 9) OrElse (e.KeyChar = 13) OrElse (e.KeyChar = 32)
  If IsLetter OrElse IsWhiteSpace OrElse IsNumber Then
    e.Handled = False
    MessageBox.Show("Just numbers and letters and whitespaces")
  End If
End Sub