asp.net奇怪的例外每三分鐘大約

Question

我想做一個非常簡單的aspx頁面，從MySQL數據庫中拉出一些數據。 頁面生成沒有問題。 （在ASPX只包含默認的形式和一個div只是打印一些數據）

Default.aspx.vb：

Imports System.Configuration 
Imports System.Data 
Imports MySql 
Imports MySql.Data 
Imports MySql.Data.MySqlClient 

Partial Class _Default 
    Inherits System.Web.UI.Page 

    Private cnstr As String =  ConfigurationManager.ConnectionStrings.Item("thisdb").ConnectionString 

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

     Dim cn As New MySqlConnection(cnstr) 
     Dim cmd As New MySqlCommand("SELECT user_firstname,user_lastname FROM tb_users;", cn) 
     cmd.CommandType = CommandType.Text 
     Dim dt As DataTable 
     dt = GetDataTableMySQL(cmd) 
     If dt.Rows.Count > 0 Then 
      testdiv.InnerHtml = dt.Rows(0).Item("user_firstname") 
      testdiv.InnerHtml += "<br/>" & dt.Rows(0).Item("user_lastname") 
     End If 
     dt.Dispose() 
     cmd.Dispose() 
     cn.Dispose() 

    End Sub 

    Private Function GetDataTableMySQL(ByVal cmd As MySqlCommand) As DataTable 
     Dim da As New MySqlDataAdapter() 
     Dim dt As New DataTable() 
     Try 
      cmd.Connection.Open() 
      da.SelectCommand = cmd 
      da.Fill(dt) 
      Return dt 
     Catch ex As MySqlException 
      Throw ex 
     Catch ex As Exception 
      Throw New Exception(ex.Message) 
     Finally 
      cmd.Connection.Close() 
      da.Dispose() 
     End Try 
    End Function 

End Class 

Web.config文件：

<?xml version="1.0"?> 
<!-- 
    For more information on how to configure your ASP.NET application, please visit 
    http://go.microsoft.com/fwlink/?LinkId=169433 
    --> 
<configuration> 
    <system.web> 
    <compilation debug="true" strict="false" explicit="true" targetFramework="4.0"> 
     <assemblies> 
     <add assembly="MySql.Data, Version=6.4.4.0, Culture=neutral, PublicKeyToken=C5687FC88969C44D"/> 
     </assemblies> 
    </compilation> 
    <customErrors mode="Off"/> 
    </system.web> 
    <connectionStrings> 
    <add name="thisdb" connectionString="Server=localhost;Database=mydatabase;Uid=mydbuser;Pwd=dbpasswd;CharSet=UTF8; "/> 
    </connectionStrings> 
</configuration> 

當我瀏覽它完美運行的頁面URL。 如果我繼續刷新頁面，一切正常，沒有問題。

現在到了惱人的問題...

如果我離開這個頁面空閒大約3-4分鐘，然後打刷新我總是得到以下異常：

The given key was not present in the dictionary.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Exception: The given key was not present in the dictionary.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[Exception: The given key was not present in the dictionary.]
_Default.GetDataTableMySQL(MySqlCommand cmd) +236 _Default.Page_Load(Object sender, EventArgs e) +112 System.Web.UI.Control.OnLoad(EventArgs e) +91
System.Web.UI.Control.LoadRecursive() +74
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272

如果我再次點擊刷新，頁面再次運行正常......等等。

後在網絡上搜索的時間，這聽起來 有關我的問題的唯一的事情，與MySQL的連接器/淨做：

連接器/網絡文件說：

Starting with MySQL Connector/Net 6.2, there is a background job that runs every three minutes and removes connections from pool that have been idle (unused) for more than three minutes. The pool cleanup frees resources on both client and server side. This is because on the client side every connection uses a socket, and on the server side every connection uses a socket and a thread.

Prior to this change, connections were never removed from the pool, and the pool always contained the peak number of open connections. For example, a web application that peaked at 1000 concurrent database connections would consume 1000 threads and 1000 open sockets at the server, without ever freeing up those resources from the connection pool.

Note, connections, no matter how old, will not be closed if the number of connections in the pool is less than or equal to the value set by the Min Pool Size connection string parameter.

好。即使這是我的問題， 這是正確的連接方式 - >獲取數據 - >斷開連接？

任何想法？這真的讓我發瘋了！

UPDATE @Andrews的建議後，我改變了功能「GetDataTableMySQL」如下：

Private Function GetDataTableMySQL(ByVal cmd As MySqlCommand) As DataTable 
    Dim dt As New DataTable 
    Using da = New MySqlDataAdapter(cmd) 
     da.Fill(dt) 
    End Using 
    Return dt 
End Function 

（它沒有解決這個問題，但我認爲這是非常有用的呈現怎樣的代碼現在看起來）

異常的堆棧跟蹤，更改爲以下：

[KeyNotFoundException: The given key was not present in the dictionary.] System.Collections.Generic.Dictionary`2.get_Item(TKey key) +9624829
MySql.Data.MySqlClient.CharSetMap.GetCharacterSet(DBVersion version, String CharSetName) +23
MySql.Data.MySqlClient.CharSetMap.GetEncoding(DBVersion version, String CharSetName) +47
MySql.Data.MySqlClient.Driver.Configure(MySqlConnection connection) +510 MySql.Data.MySqlClient.MySqlConnection.Open() +418 System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +123
System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) +166 System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) +115 _Default.GetDataTableMySQL(MySqlCommand cmd) +86
_Default.Page_Load(Object sender, EventArgs e) +112 System.Web.UI.Control.OnLoad(EventArgs e) +91
System.Web.UI.Control.LoadRecursive() +74
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

更新2看完了Connector/Net Connection String Options Reference 我測試了我的連接字符串的選項：

Pooling=false; 

，然後我測試改變池選項：

Pooling=no; 

通過測試池選項，該網頁從不起作用！ 我每次都會得到一個異常「給定的密鑰不在字典中」。

Answer 1

它可能無法解決問題，但對於DataAdapter.Fill，您不需要自己打開和關閉連接。

而且，我懷疑在try塊使用返回的 - 你可以做更多的東西一樣

Private Function GetDataTableMySQL(ByVal cmd As MySqlCommand) As DataTable 
    Dim dt As DataTable = Nothing 
    Using da = New MySqlDataAdapter() 
     da.fill(dt) 
    End Using 
    Return dt 
End Function 

，並檢查返回值狀態並沒有沒有什麼，以確保它的工作。