Question

我正在尝试我的文件上传问题的第2版。这次我想在没有存储过程的情况下测试SqlDbType与OleDbType。测试此示例时，出现错误

对象引用未设置为对象的实例

在这一行：

Dim connection As String = System.Configuration.ConfigurationManager.ConnectionStrings("Provider=""****"";user id=" & strUserID & ";data source=" & strDatabase & ";password=" & strPssWd).ConnectionString

我不明白为什么我会收到此错误（第一次使用SqlDbType）

我的表格类型如下：

byte: long raw
file_name: varchar2

Protected Sub Insert_Click(sender As Object, e As EventArgs) Handles Insert.Click

  Dim extension As String = System.IO.Path.GetExtension(FileUpload1.FileName) ' filename extension
  Dim filePath As String = Server.MapPath("~\") 'shows full path
  Dim fullPath As String = filePath + FileUpload1.FileName 'shows full path plus name
  Dim fileName As String = FileUpload1.FileName

  Dim fs As Stream = FileUpload1.PostedFile.InputStream
  Dim br As New BinaryReader(fs)
  Dim bytes As Byte() = br.ReadBytes(fs.Length)    

  Dim strQuery As String = "INSERT into t_classifieds " & "(addate, category, username, phonenbr, email, description, fulldescription, location, byte, file_name)" _
                               & " values ( val_date, val_category, val_user, val_phone, val_email, val_shortDes, val_longDes, val_location, val_byte, val_name )"

        Dim ClassifiedStr As New SqlCommand(strQuery)
        ClassifiedStr.Parameters.Add("val_date", SqlDbType.Date).Value = DateText.Text
        ClassifiedStr.Parameters.Add("val_category", SqlDbType.VarChar).Value = CategoryList.Text
        ClassifiedStr.Parameters.Add("val_user", SqlDbType.VarChar).Value = UserText.Text
        ClassifiedStr.Parameters.Add("val_phone", SqlDbType.VarChar).Value = PhoneText.Text
        ClassifiedStr.Parameters.Add("val_email", SqlDbType.VarChar).Value = EmailText.Text
        ClassifiedStr.Parameters.Add("val_shortDes", SqlDbType.VarChar).Value = ShortText.Text
        ClassifiedStr.Parameters.Add("val_longDes", SqlDbType.VarChar).Value = longText.Value
        ClassifiedStr.Parameters.Add("val_location", SqlDbType.VarChar).Value = LocationText.Text '[8]
        ClassifiedStr.Parameters.Add("val_byte", SqlDbType.Binary).Value = bytes
        ClassifiedStr.Parameters.Add("val_name", SqlDbType.Varchar).Value = fileName
        InsertUpdateData(ClassifiedStr)

End Sub

Private Sub InsertUpdateData(ClassifiedStr As SqlCommand)
    'Throw New NotImplementedException

    Dim connection As String = System.Configuration.ConfigurationManager.ConnectionStrings("Provider=""***"";user id=" & strUserID & ";data source=" & strDatabase & ";password=" & strPssWd).ConnectionString

    Dim con As New SqlConnection(connection)

    ClassifiedStr.CommandType = CommandType.Text

    ClassifiedStr.Connection = con

    con.Open()

    ClassifiedStr.ExecuteNonQuery()

    con.Close()

    con.Dispose()
End Sub

当我逐行调试时，我发现它正在运行：

? bytes

{Length=9297}
(0): 137
(1): 80
(2): 78
(3): 71
(4): 13
(5): 10
(6): 26
(7): 10
(8): 0
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(11): 13
(12): 73
(13): 72
(14): 68
(15): 82
(16): 0
(17): 0
(18): 2
(19): 176
(20): 0
(21): 0
(22): 0
(23): 128
(24): 8
(25): 2
(26): 0
(27): 0
(28): 0
(29): 124
(30): 195
(31): 205
(32): 101
(33): 0
(34): 0
(35): 0
(36): 9
(37): 112
(38): 72
(39): 89
(40): 115
(41): 0
(42): 0
(43): 14
(44): 196
(45): 0
(46): 0
(47): 14
(48): 196
(49): 1
(50): 149
(51): 43
(52): 14
(53): 27
(54): 0
(55): 0
(56): 0
(57): 7
(58): 116
(59): 73
(60): 77
(61): 69
(62): 7
(63): 223
(64): 6
(65): 23
(66): 12
(67): 49
(68): 40
(69): 151
(70): 192
(71): 200
(72): 240
(73): 0
(74): 0
(75): 0
(76): 7
(77): 116
(78): 69
(79): 88
(80): 116
(81): 65
(82): 117
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(84): 104
(85): 111
(86): 114
(87): 0
(88): 169
(89): 174
(90): 204
(91): 72
(92): 0
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(94): 0
(95): 12
(96): 116
(97): 69
(98): 88
(99): 116
< More... (The first 100 of 9297 items were displayed.) >

Answer 1

ConfigurationManager.ConnectionStrings是读取应用程序配置文件（app.config或web.config）的系统返回的字符串数组。您的连接字符串应该存储在那里并给出一个键属性以从您的应用程序中检索它

Dim connection As String = ConfigurationManager.ConnectionStrings("myConnection").ConnectionString

在你的app.config中你需要这些行

<connectionStrings>
  <add name="myConnection" connectionString="user id=xxxx;data source=yyyyyy;password=zzzzzz"
  providerName="System.Data.OracleClient" />
</connectionStrings>

当然这意味着您的连接字符串在app.config中是硬编码的，因此您无法在运行时轻松更改它。

可能的选择是班级OracleConnectionStringBuilder

使用这个类可以像这样编写一段代码

Dim builder As New OracleConnectionStringBuilder
builder("Data Source") = strDatabase 
builder("User ID") = strUserID 
builder("Password") = strPassword
Console.WriteLine(builder.ConnectionString)

SQL连接字符串错误：未将对象引用设置为对象的实例

1 个答案: