未处理InvalidCastException

问题描述

大家好！

这是编程的新手，我正在其中编写我的第一个程序，我想从sql检索数据并显示在ComboBox中，但是当我尝试运行Page_Load时却得到了(InvalidCastException未处理)，有人可以看到我的问题吗? /p>

感谢帮助

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导入System.Data.SqlClient

公共类Component_Removal
   昏暗的SqlConn作为SqlConnection
   将SqlCmd变暗为SqlCommand
   昏暗计数为整数
   昏暗查询为字符串
   昏暗的读者作为SqlDataReader

    私有子Component_Removal_Load(作为对象发送，作为EventArgs发送)处理MyBase.Load
        SqlConn =新的SqlConnection
        SqlConn.ConnectionString =
    "服务器= DESKTOP-8HE6EFV \ SQLEXPRESS;数据库= Keyn_Electronics;用户= Keyn; Pwd = keyn161;"
       昏暗的阅读器作为SqlDataReader
       试试
            SqlConn.Open()
           查询="SELECT * FROM Radio_Manufacturers"
            SqlCmd =新的SqlCommand(Query，SqlConn)
            Reader = SqlCmd.ExecuteReader
           在Reader上阅读
               昏暗的sName = Reader.GetString("numbers")
                ComboBox2.Items.Add(sName)
           结束时
            SqlConn.Close()
       捕获为SqlException
            MessageBox.Show(ex.Message)
       终于
            SqlConn.Dispose()
       结束尝试
   结束

解决方案

Hi everyone!

Completely new to programming, I am writing my first program in it I want to retrieve data from sql and display in ComboBox, but I get (InvalidCastException was unhandled) when I try to run my Page_Load can anyone see my problem?

Thanks for help

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Imports System.Data.SqlClient

Public Class Component_Removal
    Dim SqlConn As SqlConnection
    Dim SqlCmd As SqlCommand
    Dim Count As Integer
    Dim Query As String
    Dim Reader As SqlDataReader

    Private Sub Component_Removal_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        SqlConn = New SqlConnection
        SqlConn.ConnectionString =
    "Server=DESKTOP-8HE6EFV\SQLEXPRESS;Database=Keyn_Electronics;user=Keyn;Pwd=keyn161;"
        Dim Reader As SqlDataReader
        Try
            SqlConn.Open()
            Query = " SELECT * FROM Radio_Manufacturers"
            SqlCmd = New SqlCommand(Query, SqlConn)
            Reader = SqlCmd.ExecuteReader
            While Reader.Read
                Dim sName = Reader.GetString("numbers")
                ComboBox2.Items.Add(sName)
            End While
            SqlConn.Close()
        Catch ex As SqlException
            MessageBox.Show(ex.Message)
        Finally
            SqlConn.Dispose()
        End Try
    End Sub

解决方案

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