asp.net - 在调用 HttpRequest.ValidateString() 之前修改 asp 文本框

我尝试了 ONCHANGED 事件，你是对的，它最初并没有直接起作用，

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所以尝试一下，一切正常。

默认.aspx

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
  <head runat="server">
    <title></title>
  </head>
  <body>
    <form id="form1" runat="server">
      <div>
        The event TextBox1_TextChanged() is raised when the text changes in the textbox<br />
        The TextBox1_TextChanged event calls the CapitaliseText subroutine.<br />
        The Capitalisetext subroutine changes the text in textbox2 to the same as Textbox1 with the FIRST letter capitalised.<br />
        If the first letter in Textbox1 is NOT lower case then Textbox2 does not change<br />
        <br />
        All this is done without clicking the submit button.<br />
        The code runs on the server not the client.<br />
        <br />
        <br />
        Textbox1 -
        <asp:TextBox ID="TextBox1" runat="server" AutoPostBack="True" ViewStateMode="Enabled"></asp:TextBox>
        <br />
        <br />
        Textbox-2 - <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
        <br />
        <br />
        <br />
        <br />
        Submit Form -
        <asp:Button ID="Button1" runat="server" Text="Submit Form" />
        <br />
        <br />
        <br />
        <br />
        Textbox2 Contains -
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
        <br />
        <br />
      </div>
    </form>
  </body>
</html>

默认.aspx.vb

Partial Class _Default
  Inherits System.Web.UI.Page

  Dim FormWasSubmitted As Boolean

  Protected Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
    'run my regex
    CapitaliseText(sender, e)
  End Sub

  Sub CapitaliseText(sender As Object, e As EventArgs)
    '
    Dim XString As String

    'get textbox1.text
    XString = sender.Text
    If Trim(XString) <> "" Then
      'if first chracter is not caps
      If (Char.IsLower(XString.Chars(0))) Then
            TextBox2.Text = Char.ToUpper(XString.Chars(0)) + XString.Substring(1, XString.Length - 1)
        UpdateLabel()
      End If
    End If
  End Sub

  Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    FormWasSubmitted = True
    UpdateLabel()
  End Sub

  Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    UpdateLabel()
  End Sub

  Sub UpdateLabel()
    If FormWasSubmitted Then
      If Trim(TextBox2.Text) <> "" Then
        Label1.Text = TextBox2.Text & "[Submitted]"
      Else
        Label1.Text = "Nothing"
      End If
    Else
      If Trim(TextBox2.Text) <> "" Then
        Label1.Text = TextBox2.Text
      Else
        Label1.Text = "Nothing"
      End If
    End If
  End Sub
End Class

注意文本框的定义包括

自动回发 = 真
ViewStateMode = 启用

由于我不知道您在提交表单后正在执行什么处理，因此它可能无法正常工作（？）

不过在那个例子中它工作得很好。看看这是否有帮助，不要忘记阅读引用的链接

Netframework-4.7.2#System_Web_UI_WebControls_TextBox_OnTextChanged_System_EventArgs_

asp.net - 在调用 HttpRequest.ValidateString() 之前修改 asp 文本框

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