SQL Connection String Error: Object reference not set to an instance of an object

Question

我正在尝试文件上传问题的版本 2。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

Object reference not set to an instance of an object

这一行：

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

我不明白为什么会出现此错误（第一次使用 SqlDbType）

我的table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，我可以看到它正在运行：

? bytes

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< More... (The first 100 of 9297 items were displayed.) >

Answer 1

ConfigurationManager.ConnectionStrings 是系统读取您的应用程序配置文件（app.config 或 web.config）返回的字符串数组。您的连接字符串应存储在那里并提供一个密钥属性以从您的应用程序

中检索它

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

并且在您的 app.config 中您需要有这些行

<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易更改它。

一个可能的选择是 class OracleConnectionStringBuilder

有了这个class就可以写出这样一段代码

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

SQL Connection String Error: Object reference not set to an instance of an object

SQL Connection String Error: Object reference not set to an instance of an object

vb.net

file-upload

oracle10g

sqlconnection