System.Data.SQLite

LoadExtension("SQLite.Interop.dll", "sqlite3_fts_init");

System.Data.SQLite.SQLiteException occurred
  HResult=-2147467259
  Message=SQL logic error or missing database
error during initialization:
  Source=System.Data.SQLite
  ErrorCode=1
  StackTrace:
       at System.Data.SQLite.SQLite3.LoadExtension(String fileName, String procName)
       at ApplicationServices.Factories.ConnectionDataFactory.<CreateConnectionAsync>d__9.MoveNext() in C:\Dropbox\SoftLAnd\Project\VS13\TOTKSilverlight\Goods\ApplicationServices\Factories\ConnectionDataFactory.cs:line 111
  InnerException:

connection.Pooling = true;
recreateconnection

I'm a bit confused about this ticket.  First, when calling the LoadExtension
method, you will almost certainly need to pass the fully qualified path to the
"SQLite.Interop.dll" file.  Also, I have a couple questions:

1. Which extension are you trying to load?

2. Are you actually using connection pooling?

Example defect code.
using System;
using System.Linq;
using System.Data.SQLite;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var cs = "data source=:memory:;pooling=True;";
            var path = Environment.Is64BitProcess ? "x64" : "x86";
            var dllFullFileName = Path.Combine(path, "SQLite.Interop.dll");
            foreach (var i in Enumerable.Range(0, 10))
            {
                using (var connection = new SQLiteConnection(cs))
                {
                    connection.Open();
                    connection.EnableExtensions(true);
                    connection.LoadExtension(dllFullFileName, "sqlite3_fts5_init");
                    connection.EnableExtensions(false);
                }
            }
        }
    }
}

Off hand, I can tell you that connection pooling does not interact well with the
load extension mechanism.  I think System.Data.SQLite prevents connections that
use extensions from entering (or re-entering) the pool.

Ok, I appear to be wrong.  It's CreateModule that disables the pool.

Thanks for the example code.  Reproduced the error message locally.

The root cause of the error is trying to load an extension into a connection that
already has it (i.e. due to it being from the pool).  To be specific:

1. Connection #1 is opened fresh.

2. Connection #1 loads the FTS5 extension.

3. Connection #1 is closed -AND- added to the connection pool.

4. Connection #2 is opened from the pool (with FTS5 already loaded).

5. An attempt is made to load the FTS5 extension into Connection #2.

6. Exception is thrown.

I see three workarounds to this issue:

1. Avoid using Pooling=True when you plan to load extensions.

2. Check if an extension is already loaded prior to calling LoadExtension
   (e.g. by trying to use something that it adds to the connection).

3. Wrap the LoadExtension calls in a try/catch and ignore exceptions (this is
   the most problematic workaround because LoadExtension can fail for reasons
   other than the extension already being loaded).