SQLite keeps the database locked even after the connection is closed

Question

I\'m using System.Data.SQLite provider in an ASP.NET application (framework 4.0). The issue I\'m running into is that when I INSERT something in a table in the SQLite databa

Answer 1

I was only having the problems mentioned here when locking the computer, even after unlocking it, was working fine otherwise lucky cuz i just started locking it lately and the software just released couple days ago before anyone knows about it.

Anyway i had all the stuff like closing connections and ClearAllPools etc but was missing aTableAdapter.Adapter.Dispose() and that fixed it.

Answer 2

In my case I was creating SQLiteCommand objects without explicitly disposing them.

var command = connection.CreateCommand();
command.CommandText = commandText;
value = command.ExecuteScalar();

I wrapped my command in a using statement and it fixed my issue.

static public class SqliteExtensions
{
    public static object ExecuteScalar(this SQLiteConnection connection, string commandText)
    {
        // Added using
        using (var command = connection.CreateCommand())
        {
            command.CommandText = commandText;
            return command.ExecuteScalar();
        }
    }
}

Then you can use it like this

connection.ExecuteScalar(commandText);

Answer 3

In most cases the problem will arise if you don't dispose your readers and commands properly. There is a scenario in which commands and readers will not dispose properly.

Scenario 1: In case you are running a boolean function. before a result is reached the code in the finally block will not excecute. This is a big problem if you are going to be evaluating the results of function isDataExists while executing code if it suits the result i.e

    if(isDataExists){
        // execute some code
    }

The function being evaluated

    public bool isDataExists(string sql)
    {
        try
        {
            OpenConnection();
            SQLiteCommand cmd = new SQLiteCommand(sql, connection);
            reader = cmd.ExecuteReader();
            if (reader != null && reader.Read())
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        catch (Exception expMsg)
        {
            //Exception
        }
        finally
        {
            if (reader != null)
            {
                reader.Dispose();
            }
            CloseConnection();
        }
        return true;
    }

Solution: Dispose your reader and command inside the try block as follows

            OpenConnection();
            SQLiteCommand cmd = new SQLiteCommand(sql, connection);
            reader = cmd.ExecuteReader();
            if (reader != null && reader.Read())
            {
                cmd.Dispose();
                CloseConnection();
                return true;
            }
            else
            {
                cmd.Dispose();
                CloseConnection();
                return false;
            }

Finally dispose the reader and command just in case some thing went wrong

        finally
        {
            if (reader != null)
            {
                reader.Dispose();
            }
            CloseConnection();
        }

Answer 4

The following worked for me: MySQLiteConnection.Close(); SQLite.SQLiteConnection.ClearAllPools()

Answer 5

Had the same problem. Solved it simply by installing SQLite 1.0.111 (via nuget).

Did not have to change anything on my code, only update to that version. Previously I used 1.0.85 where the file was locked, although the connection was closed and disposed.

Answer 6

I found edymtt's answer right about blaming TableAdapters / Datasets, but instead of modifying the every time re-generated TableAdapter codefile, I found an other solution: to manually call .Dispose on the TableAdapter's child elements. (In .NET 4.5, latest SQLite 1.0.86)

using (var db = new testDataSet())
{
    using (testDataSetTableAdapters.UsersTableAdapter t = new testDataSetTableAdapters.UsersTableAdapter())
    {
        t.Fill(db.Users);
        //One of the following two is enough
        t.Connection.Dispose(); //THIS OR
        t.Adapter.Dispose();    //THIS LINE MAKES THE DB FREE
    }
    Console.WriteLine((from x in db.Users select x.Username).Count());
}