You receive an "unspecified error" error message when you create more than 64 connections to an Access Database in one process

If you connect to a Microsoft Access database and then you create more than 64 connections in one process, you may receive one of the following error messages:

• In Microsoft Visual Studio .NET:
  Unspecified error
• In Microsoft Visual Basic 6.0, if you use ActiveX Data Objects (ADO):
  Runtime-Error '-2147467259 (80004005)': Unspecified Error

This behavior is by design.

Steps to reproduce the behavior

1. Start Visual Studio .NET.
2. Use Microsoft Visual C# .NET or Microsoft Visual Basic .NET to create a new Console Application project. Name the project AccessApplication. By default, Class1.cs (in Visual C# .NET) or Module1.vb (in Visual Basic .NET) is created.
3. In Class1.cs or in Module1.vb, replace the existing code with following code.
   
   Note To use this sample code, change the Data Source path to the path of any Microsoft Access database file that is on your computer.
   
   Visual C# .NET Code

   using System;
   using System.Data.OleDb;
   
   namespace AccessApplication
   {
   	/// <summary>
   	/// Summary description for Class1.
   	/// </summary>
     class Class1
     {
       /// <summary>
       /// The main entry point for the application.
       /// </summary>
       [STAThread]
       static void Main(string[] args)
       {
         //
         // TODO: Add code to start application here
         //
         int intCount;
         int intMaxConnections;
         string strConnection;
   
         intMaxConnections = 65;
         object[] objArray = new object[intMaxConnections];
   
         strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;" + 
           "Data Source=C:\\Program Files\\Microsoft Office\\Office10\\Samples\\Northwind.mdb;";
   			        
         Console.WriteLine("Starting test...");
   			
         for (intCount=0;intCount<intMaxConnections;intCount++)
         {
           try
           {
             OleDbConnection myConnection = new OleDbConnection(strConnection);
             myConnection.Open();
             Console.WriteLine("Open connection is " + intCount);
             objArray[intCount] = myConnection;
           }
           catch(Exception excpt)
           {
             Console.WriteLine("Exception : " + excpt.Message.ToString());
           }
         }
       }        
     }
   }
   

   Visual Basic .NET Code

   Imports System.Data.OleDb
   Module Module1
   
     Sub Main()
       Dim intCount As Integer
       Dim intMaxConnections As Integer
       Dim strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;" _
           & "Data Source=C:\Program Files\Microsoft " _
           & "Office\Office10\Samples\Northwind.mdb;"
   
       intMaxConnections = 65
   
       Dim IntArray(intMaxConnections) As Object
       Console.WriteLine("Starting test...")
       For intCount = 0 To intMaxConnections
         Try
           Dim objConnection As New OleDbConnection(strConnection)
           objConnection.Open()
           Console.WriteLine("Open connection is " & intCount)
           IntArray(intCount) = objConnection
         Catch excpt As Exception
           Console.WriteLine("Exception " + excpt.Message.ToString())
         End Try
       Next
     End Sub
   
   End Module
   

4. On the Debug menu, click Start.

For more information about how to open an Access database by using ADO, visit the following Microsoft Developer Network (MSDN) Web site: