31 December 2016 DbProviderFactory, ADO.NET, SQL Robert Muehsig

Recently I needed to write a module that needs to connect to a wide range of SQL-DBs, e.g. MySQL, MS SQL, Oracle etc.

Problem: Most providers will use their concret classes

If you look at the C# example on the MySQL dev page you will see the MsSql-Namespace and classes:

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection();
    conn.ConnectionString = myConnectionString;
    conn.Open();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message);
}

The same classes will probably not work for a MS SQL database.

“Solution”: Use the DbProviderFactories

For example if you install the MySql-NuGet package you will also get this little enhancement to you app.config:

<system.data>
  <DbProviderFactories>
    <remove invariant="MySql.Data.MySqlClient" />
    <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />
  </DbProviderFactories>
</system.data>

Now we can get a reference to the MySql client via the DbProviderFactories:

using System;
using System.Data;
using System.Data.Common;

namespace DbProviderFactoryStuff
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("All registered DbProviderFactories:");
                var allFactoryClasses = DbProviderFactories.GetFactoryClasses();

                foreach (DataRow row in allFactoryClasses.Rows)
                {
                    Console.WriteLine(row[0] + ": " + row[2]);
                }

                Console.WriteLine();
                Console.WriteLine("Try to access a MySql DB:");

                DbProviderFactory dbf = DbProviderFactories.GetFactory("MySql.Data.MySqlClient");
                using (DbConnection dbcn = dbf.CreateConnection())
                {
                    dbcn.ConnectionString = "Server=localhost;Database=testdb;Uid=root;Pwd=Pass1word;";
                    dbcn.Open();
                    using (DbCommand dbcmd = dbcn.CreateCommand())
                    {
                        dbcmd.CommandType = CommandType.Text;
                        dbcmd.CommandText = "SHOW TABLES;";

                        // parameter...
                        //var foo = dbcmd.CreateParameter();
                        //foo.ParameterName = "...";
                        //foo.Value = "...";

                        using (DbDataReader dbrdr = dbcmd.ExecuteReader())
                        {
                            while (dbrdr.Read())
                            {
                                Console.WriteLine(dbrdr[0]);
                            }
                        }
                    }
                }
            }
            catch (Exception exc)
            {
                Console.WriteLine(exc.Message);
            }

            Console.ReadLine();

        }
    }
}

The most important line is this one:

DbProviderFactory dbf = DbProviderFactories.GetFactory("MySql.Data.MySqlClient");

Now with the DbProviderFactory from the MySql client we can access the MySql database without using any MySql-specific classes.

There are a couple of “in-built” db providers registered, like the MS SQL provider or ODBC stuff.

The above code will output something like this:

All registered DbProviderFactories:
Odbc Data Provider: System.Data.Odbc
OleDb Data Provider: System.Data.OleDb
OracleClient Data Provider: System.Data.OracleClient
SqlClient Data Provider: System.Data.SqlClient
Microsoft SQL Server Compact Data Provider 4.0: System.Data.SqlServerCe.4.0
MySQL Data Provider: MySql.Data.MySqlClient

Other solutions

Of course there are other solutions - some OR-Mapper like the EntityFramework have a provider model which might also work, but this one here is a pretty basic approach.

SQL Commands

The tricky bit here is that you need to make sure that your SQL commands work on your database - this is not a silver bullet, it just lets you connect and execute SQL commands to any ‘registered’ database.

The full demo code is also available on GitHub.

Hope this helps.


Written by Robert Muehsig

Software Developer - from Dresden, Germany, now living & working in Switzerland. Microsoft MVP & Web Geek.
Other Projects: KnowYourStack.com |ExpensiveMeeting | EinKofferVollerReisen.de


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