Question

我实在无法相信我无法找到这样的答案。

Public NotInheritable Class Tester
    Public Shared Sub changeText(ByVal TextBoxControl As Windows.Forms.TextBoxBase)
        Dim testString As String = TextBoxControl.Text
        testString = "Changed!"
    End Sub
End Class

我希望testString成为TextBoxControl.Text的指针。但是，TextBoxControl.Text未更改。相反，它出现

Dim testString As String = TextBoxControl.Text

相当于

Dim testString As String = TextBoxControl.Text.Clone()

但我不想要这种行为。我只想要引用TextBoxControl的{{1}}属性。我可以这样做吗？为什么不通过引用传递字符串？

Answer 1

你无法做你想做的事。字符串在.NET和Java中都是不可变的。您的示例也不适用于Java。

Answer 2

这会有效，因为你将传递变量inref：

Public NotInheritable Class Tester
    Public Shared Sub changeText(ByRef str As String)
       str = "Changed!"
    End Sub
End Class

并称之为：

Tester.changeText(myTextbox.Text)

Answer 3

较短的方式如下，但你所追求的是什么？

Public NotInheritable Class Tester
    Public Shared Sub changeText(ByVal TextBoxControl As Windows.Forms.TextBoxBase)
        Dim testString As String = "Changed!"        
   End Sub
End Class

如果要将复制文本框条目复制到标签，请使用以下示例。我直接从文本框中复制并通过字符串：

.aspx.vb代码

Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Label1.Text = TextBox1.Text

        Dim vString = TextBox1.Text

        Label5.Text = vString
    End Sub
End Class

.aspx代码

<%@ 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">
          <asp:Label ID="Label2" runat="server" Text="Add new text:"></asp:Label>
        <p> </p>
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
           <p> </p>
        <asp:Button ID="Button1" runat="server" Text="Copy text to label" />
           <p> </p>
         <asp:Label ID="Label3" runat="server" Text="Result from textbox:"></asp:Label>
        <asp:Label ID="Label1" runat="server" Text=""></asp:Label>

          <p> </p>
         <asp:Label ID="Label4" runat="server" Text="Result from string:"></asp:Label>
        <asp:Label ID="Label5" runat="server" Text=""></asp:Label>
    <div>

    </div>
    </form>
</body>
</html>

如何在VB.NET中通过引用传递String

3 个答案: