Asp.net 连接字符串正确时出现实例失败错误

我在页面加载事件中有以下代码:

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

        con = New SqlConnection("Data Source=14GRAFICALI\\SQLEXPRESS;Initial Catalog=sagar;Integrated Security=True")
        '-----------------------fill name ddl------------------------------'

        Try

            da = New SqlDataAdapter("select EmpName from empMaster_VB", con)
            ds = New DataSet()
            da.Fill(ds)
            For i As Integer = 0 To ds.Tables(0).Rows.Count

                ddlName.Items.Add(ds.Tables(0).Rows(i)(0).ToString())

            Next


        Catch ex As Exception

        End Try

        '--------------------------------------------------------------------'


        '----------------fill expence-------------------------------------'

        Try

            da = New SqlDataAdapter("select ExpName from expenceType_VB", con)
            ds = New DataSet()
            da.Fill(ds)
            For i As Integer = 0 To ds.Tables(0).Rows.Count

                ddlExpence.Items.Add(ds.Tables(0).Rows(i)(0).ToString())

            Next


        Catch ex As Exception

        End Try


        '---------------------------------------------------------------'



    End Sub

此代码用于使用数据库表中的名称和费用值填充下拉列表.

我在执行代码时出现"instance failure"错误.

我判断了answers个堆栈中的一个，并判断了我的连接字符串.但是，我的连接字符串也是正确的.

如果此代码中缺少任何其他内容，请帮助我.