输入正确格式的字符串。 VB.net - 新手需要帮助

Question

i am having some issues with a page and the code behind i am working on. please see the code:

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

        Dim dtTable As DataTable = Nothing
        Dim intConnectionId As Integer = 0

        If  Page.IsPostBack Then

            ' Get user data from session
            With HttpContext.Current

                intConnectionId = CInt(result.Value)
            End With
        End If

        ' Remove connection
        modConnections.Delete(intConnectionId)

        ' Clear desks attahced to connection
        modDeskText.ClearUserDesk(intConnectionId)

        Using sqlCommand As New SqlCommand
            With sqlCommand
                .CommandText = "usp_connectsdetailedlist"
                .CommandType = CommandType.StoredProcedure
            End With

            Execute(sqlCommand, dtTable)
        End Using

        With Rep1
            .DataSource = dtTable.DefaultView
            .DataBind()
        End With

        If Not IsNothing(dtTable) Then
            dtTable.Dispose()
        End If

    End Sub

[FormatException: Input string was not in a correct format.]
   Microsoft.VisualBasic.CompilerServices.Conversions.ParseDouble(String Value, NumberFormatInfo NumberFormat) +213
   Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(String Value) +90

[InvalidCastException: Conversion from string "" to type 'Integer' is not valid.]
   Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(String Value) +238
   frmConnects2.Page_Load(Object sender, EventArgs e) in D:\Source Code\PTS\PTS Online .NET - Copy\PTS Online .NET\PTS Online .NET stu\frmConnects2.aspx.vb:17
   System.Web.UI.Control.OnLoad(EventArgs e) +95
   System.Web.UI.Control.LoadRecursive() +59
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +678

On the line:

intConnectionId = CInt(result.Value) 

I am getting the above error. No matter what i do i cannot get the data to convert to the format i need to work. I now understand this has nothing to do with the right hand side code.

My goal is to get the data from a table, place in into the text box ( <input type="text" id="result" runat="server" /> ) id="result" and then use the "id" of the record selected in SQL to remove the connection. see table below:

<ItemTemplate> 
                        <tr class="<%# ReturnValuesAsColor(Eval("online"), Eval("mobile"), Eval("server_proc"))%>">
                        <td><%# Eval("id").ToString%></td>
                        <td><%# Eval("user_id").ToString%></td>
                        <td><%# Eval("user_name").ToString%></td>
                        <td><%# Eval("workstation_name").ToString%></td>
                        <td><%# Eval("ip_address").ToString%></td>
                        <td><%# Eval("connect_date").ToString%></td>
                        <td><%# Eval("refresh_date").ToString%></td>
                        <td><%# Eval("app_ver").ToString%></td>
                        <td><%# Eval("app_date").ToString%></td>
                        <td><%# CBool(Eval("get_messages_flag")).ToString%></td>
                        <td><%# FixNumbers(Eval("message_type_flags"))%></td>
                        <td><%# Eval("online").ToString%></td>
                        <td><%# Eval("mobile").ToString%></td>
                        <td><%# Eval("group_name").ToString%></td>
                        <td><%# Eval("server_proc").ToString%></td>
                        <td><input type="submit" class="ui-button ui-widget ui-state-default ui-corner-all" value="delete connection" onclick="clearText(result); CopyId(<%# Eval("id").ToString%>);" /></td>
                        </tr>

                    </ItemTemplate>

JS used:

<script> 
                function CopyId(num) {
                    var txt = document.getElementById("<%= result.ClientID%>").value;
                    txt = num;
                    document.getElementById("<%= result.ClientID%>").value = txt;
                    }
 </script>

Sorry if i missed anything or there is a lack of info. Any help much appreciated.

Answer 1

You haven't shown us the definition for result or result.Value so this is an educated guess.

Try testing for a null value in the database:

If IsDbNull(result.Value) Then
    intConnectionId = 0 
Else
    intConnectionId = CInt(result.Value)
End If

Answer 2

in VB you need to check your variable to ensure it is not empty, null, & nothing and does not contain any non numeric characters. I'd also use CTYPE and Trim. The Conversion will only work if the string contains a numeric value. If you are having a problem populating the string then you need to check the code where it's populated. I'm afraid I don't know JS.