Question

我在页面加载时选择数据库中的值到文本框中。然后，当我更改它们并想要更新数据库时，值与原始值相同。例如，我将名称 Robin Hood 选择为TextBoxName，将其更改为 Bill Gates ，但更新时文本框的值仍为 Robin Hood 。我该如何解决这个问题？

但是，这仅适用于TextMode="SingleLIne"或"MultiLine“的文本框。例如，当文本框中包含TextMode="Url"时，它可以正常工作。

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 'Bind
    Try
        Using conn As New SqlConnection(connStr)
            Dim cmd As SqlCommand = conn.CreateCommand
            cmd.CommandText = "SELECT * FROM Profiles WHERE (ProfileId = @ProfileId)"
            cmd.Parameters.AddWithValue("@ProfileId", Request.QueryString("id"))
            conn.Open()
            Dim rd As SqlDataReader = cmd.ExecuteReader()
            While rd.Read()
                ProfileImage.ImageUrl = rd.Item("ProPicUrl")
                txtName.Text = rd.Item("Name")
                txtCity.Text = rd.Item("City")
                drpRegion.Items.FindByText(rd.Item("Region")).Selected = True
                txtAge.Text = rd.Item("Age")
                RadioButtonList1.Items.FindByText(rd.Item("Sex")).Selected = True
                txtLink.Text = rd.Item("Link")
                txtPhone.Text = rd.Item("Phone")
                txtAbout.Text = rd.Item("About")
                txtMotto.Text = rd.Item("Motto")
                txtGoal.Text = rd.Item("Goal")
                txtHobby.Text = rd.Item("Hobby")
            End While
            conn.Close()
        End Using
    Catch ex As Exception

    End Try
End Sub

Protected Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
    Dim fileUrl As String = "~/ProPics/"
    Dim name As String = txtName.Text
    Try
        'Save profile picture
        Try
            If FileUpload1.HasFile Then
                fileUrl += FileUpload1.FileName
                FileUpload1.SaveAs(Server.MapPath(fileUrl))
            Else
                fileUrl = ProfileImage.ImageUrl
            End If
        Catch ex As Exception
            UploadMessage.Text = "Nastala chyba při nahrávání obrázku." + vbCrLf + "Chybové hlášení: " + ex.Message
        End Try

        Using conn As New SqlConnection(connStr)
            Dim cmd As SqlCommand = conn.CreateCommand
            cmd.CommandText = "UPDATE Profiles SET Name = @Name, ProPicUrl = @Url, City = @City, Region = @Region, Age = @Age, Sex = @Sex, Link = @Link, Phone = @Phone, About = @About, Motto = @Motto, Goal = @Goal, Hobby = @Hobby WHERE (ProfileId = @ProfileId)"
            cmd.Parameters.AddWithValue("@Url", fileUrl)
            cmd.Parameters.AddWithValue("@Name", name)
            cmd.Parameters.AddWithValue("@City", txtCity.Text)
            cmd.Parameters.AddWithValue("@Region", drpRegion.SelectedItem.Text)
            cmd.Parameters.AddWithValue("@Age", txtAge.Text)
            cmd.Parameters.AddWithValue("@Sex", RadioButtonList1.SelectedItem.Text)
            cmd.Parameters.AddWithValue("@Phone", txtPhone.Text)
            cmd.Parameters.AddWithValue("@Link", txtLink.Text)
            cmd.Parameters.AddWithValue("@About", txtAbout.Text)
            cmd.Parameters.AddWithValue("@Motto", txtMotto.Text)
            cmd.Parameters.AddWithValue("@Goal", txtGoal.Text)
            cmd.Parameters.AddWithValue("@Hobby", txtHobby.Text)
            cmd.Parameters.AddWithValue("@ProfileId", Request.QueryString("id"))
            conn.Open()
            cmd.ExecuteNonQuery()
            conn.Close()
            'Refresh page
            Response.Redirect(Request.RawUrl)
        End Using
    Catch ex As Exception

    End Try
End Sub

Answer 1

在Page_Load事件中执行代码时，需要添加对页面IsPostBack属性的检查。

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    if Not PostBack Then

       ...... code to execute only the first time the Page_Load is called

       Try


       End Try
       Catch ex As Exception

       End Try
    End If 

    .. code to execute every time....

End Sub

当您的用户点击带有Runat=Server的按钮时，该按钮会在服务器端代码上调用该事件，但这会导致对Page_Load的新调用。

实际上，每次执行Page_Load事件时，您的代码都会从数据库重新加载原始值，因此您的按钮单击事件代码会从数据库中看到原始值而不是修改后的值。

Page Life Cycle上的这篇文章在这里很有用

文本框中的值在update语句中始终相同

1 个答案: