How do I handle Database Connections with Dapper i

Question

I've been playing with Dapper, but I'm not sure of the best way to handle the database connection.

Most examples show the connection object being created in the example class, or even in each method. But it feels wrong to me to reference a connection string in every clss, even if it's pulling from the web.config.

My experience has been with using a DbDataContext or DbContext with Linq to SQL or Entity Framework, so this is new to me.

How do I structure my web apps when using Dapper as my Data Access strategy?

Answer 1

I created extension methods with a property that retrieves the connection string from configuration. This lets the callers not have to know anything about the connection, whether it's open or closed, etc. This method does limit you a bit since you're hiding some of the Dapper functionality, but in our fairly simple app it's worked fine for us, and if we needed more functionality from Dapper we could always add a new extension method that exposes it.

internal static string ConnectionString = new Configuration().ConnectionString;

    internal static IEnumerable<T> Query<T>(string sql, object param = null)
    {
        using (SqlConnection conn = new SqlConnection(ConnectionString))
        {
            conn.Open();
            return conn.Query<T>(sql, param);
        }
    }

    internal static int Execute(string sql, object param = null)
    {
        using (SqlConnection conn = new SqlConnection(ConnectionString))
        {
            conn.Open();
            return conn.Execute(sql, param);
        }
    }

Answer 2

Hi @donaldhughes I'm new on it too, and I use to do this: 1 - Create a class to get my Connection String 2 - Call the connection string class in a Using

Look:

DapperConnection.cs

public class DapperConnection
{

    public IDbConnection DapperCon {
        get
        {
            return new SqlConnection(ConfigurationManager.ConnectionStrings["Default"].ToString());

        }
    }
}

DapperRepository.cs

  public class DapperRepository : DapperConnection
  {
       public IEnumerable<TBMobileDetails> ListAllMobile()
        {
            using (IDbConnection con = DapperCon )
            {
                con.Open();
                string query = "select * from Table";
                return con.Query<TableEntity>(query);
            }
        }
     }

And it works fine.

Answer 3

I wrap connection with the helper class:

public class ConnectionFactory
{
    private readonly string _connectionName;

    public ConnectionFactory(string connectionName)
    {
        _connectionName = connectionName;
    }

    public IDbConnection NewConnection() => new SqlConnection(_connectionName);

    #region Connection Scopes

    public TResult Scope<TResult>(Func<IDbConnection, TResult> func)
    {
        using (var connection = NewConnection())
        {
            connection.Open();
            return func(connection);
        }
    }

    public async Task<TResult> ScopeAsync<TResult>(Func<IDbConnection, Task<TResult>> funcAsync)
    {
        using (var connection = NewConnection())
        {
            connection.Open();
            return await funcAsync(connection);
        }
    }

    public void Scope(Action<IDbConnection> func)
    {
        using (var connection = NewConnection())
        {
            connection.Open();
            func(connection);
        }
    }

    public async Task ScopeAsync<TResult>(Func<IDbConnection, Task> funcAsync)
    {
        using (var connection = NewConnection())
        {
            connection.Open();
            await funcAsync(connection);
        }
    }

    #endregion Connection Scopes
}

Examples of usage:

public class PostsService
{
    protected IConnectionFactory Connection;

    // Initialization here ..

    public async Task TestPosts_Async()
    {
        // Normal way..
        var posts = Connection.Scope(cnn =>
        {
            var state = PostState.Active;
            return cnn.Query<Post>("SELECT * FROM [Posts] WHERE [State] = @state;", new { state });
        });

        // Async way..
        posts = await Connection.ScopeAsync(cnn =>
        {
            var state = PostState.Active;
            return cnn.QueryAsync<Post>("SELECT * FROM [Posts] WHERE [State] = @state;", new { state });
        });
    }
}

So I don't have to explicitly open the connection every time. Additionally, you can use it this way for the convenience' sake of the future refactoring:

var posts = Connection.Scope(cnn =>
{
    var state = PostState.Active;
    return cnn.Query<Post>($"SELECT * FROM [{TableName<Post>()}] WHERE [{nameof(Post.State)}] = @{nameof(state)};", new { state });
});

What is TableName<T>() can be found in this answer.