Question

我想更改文本框信息但是当我尝试这样做时，它不会工作这是我的asp.net vb代码

Imports System.Data.SqlClient

导入System.Data Imports System.Data.SqlClient.SqlDataReader 部分类_Default 继承System.Web.UI.Page

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

    Dim connectionString As String = "Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\napster\Documents\ZE.mdf;Integrated Security=True;Connect Timeout=30"



    Dim queryString As String = "Update TEST Set chaine1= '" & TextBox1.Text & "' "
    Dim connection As New SqlConnection(connectionString)

    Dim command As New SqlCommand(queryString, connection)

    connection.Open()
    command.ExecuteNonQuery()
    connection.Close()

End Sub

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    Dim connectionString As String = "Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\napster\Documents\ZE.mdf;Integrated Security=True;Connect Timeout=30"
    Dim queryString As String = "SELECT * from TEST "
    Dim connection As New SqlConnection(connectionString)

    Dim command As New SqlCommand(queryString, connection)

    connection.Open()
    Dim dataReader As SqlDataReader = command.ExecuteReader()

    While dataReader.Read()
        TextBox1.Text = dataReader.GetSqlString(3)
    End While
    TextBox1.
End Sub

结束班

Answer 1

您应该始终考虑ASP.NET模型的工作原理。

在ASP.NET中，当您单击执行服务器端代码（事件）的按钮时，在调用事件处理程序代码之前始终会调用Page.Load事件。

在您的Page.Load中再次执行代码以从数据库加载TextBox，但此代码会破坏您键入的文本框的内容。文本框设置为数据库提取的原始值，因此，当执行按钮事件处理程序中的代码时，它会将相同的值写入数据库。

要解决此问题，您需要将其添加到Page_Load事件

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    if Not IsPostBack Then
        Dim connectionString As String = "......"
        Dim queryString As String = "SELECT * from TEST "
        Dim connection As New SqlConnection(connectionString)
        Dim command As New SqlCommand(queryString, connection)

        connection.Open()
        Dim dataReader As SqlDataReader = command.ExecuteReader()

        While dataReader.Read()
            TextBox1.Text = dataReader.GetSqlString(3)
        End While
   End If
End Sub

说，请注意，按钮单击事件中的代码非常危险，因为您将用户输入的内容连接到一个字符串，然后将该字符串作为sql命令传递给数据库。这是Sql Injection attacks使用的模式，可能会破坏您的数据库或从您的表中窃取有价值的信息

使用datareader的asp.net更新不起作用

1 个答案: