I was pointed to the Passionate programmer by one of the blog posts at Los Techies. I'm about a third through the book and so far it has been a real joy to read!

It's full of good tips on how to alter your behavior to become something better as a programmer. I'm probably going to write some posts on what I've done with the various "act on it!", but in the meantime, go get it and start reading!

Just a quick update on my previous posting following one of the comments made by den Ben

just out of curiosity... why wouldn't you
dispatcher.Add<SaveDocumentRequest>(s =>
{
s.Document = document;
s.UserID = userID;
});

He's absolutely right. Using a Func forced me to (mis)use the params keyword as you are not allowed  to use the above syntax with the old code:

public virtual IDispatcher Add<TRequestType>(params Func<TRequestType, object>[] funcs)
    where TRequestType : Request, new()
{
    TRequestType request = new TRequestType();
    foreach (var func in funcs)
    {
        func.Invoke(request);
    }
    AddRequest(request, false);
    return this;
}

I actually had noticed the code not using the return value by the func but disregarded it as I was a bit too happy with the "elegance" of my inital solution.

But I think (and I think you'll agree) that using an Action is much cleaner here:

public virtual IDispatcher Add<TRequestType>(Action<TRequestType> action)
    where TRequestType : Request, new()
{
    TRequestType request = new TRequestType();
    action(request);
    AddRequest(request, false);
    return this;
}

Thanks den Ben!

One of my colleagues asked me today if I could write a utility function that would make his life more easy.

The objective was to call a stored procedure n-times for every item in a list. Of course some of the properties on every item had to be mapped to parameters in the stored procedure.

The desired syntax would be something like:

builder.SetStoredProcedureNameTo( " some sproc name ")
        .Execute ( customerList ,
            (s,t) => s.AddParameterWIthValue( parameterName, t.PROPERTY_NAME_1) ,
            (s,t) => s.AddParameterWIthValue( parameterName, t.PROPERTY_NAME_2) ,
             (s,t) => s.AddParameterWIthValue( parameterName, t.PROPERTY_NAME_3)
      );

I already have a fluent wrapper class to make our ADO.Net a bit more friendly, the interface looks like:

public interface ICustomSqlCommandBuilder
{
    ICustomSqlCommandBuilder SetStoredProcedureNameTo(string storedProcedureName);
    ICustomSqlCommandBuilder AddParameterWithValue(string parameterNameInDatabase, object value);
    ICustomSqlCommandBuilder AddExlicitOutputIntParameterToTheCommandFor(string parameterName);
    ICustomSqlCommandBuilder AddExlicitOutputDateTimeParameterToTheCommandFor(string parameterName);

    IList<TReturnType> ExecuteReaderFor<TReturnType>()
        where TReturnType : new();
}

Nothing special except for the ExecuteReaderFor<TReturnType>() but that's for another post.

Having the fluent interface on ICustomSqlCommandBuilder combined with the lambda magic explained in this post I came up with the following signature:

ICustomSqlCommandBuilder ExecuteScalarForThisList<T>(
    IList<T> list,
    params Action<ICustomSqlCommandBuilder, T>[] actionList);

(s, t) => s.AddParameterWithValue("parameterName", t.PROPERTY_NAME)

to every property in the object<T> that needs to be mapped against a parameter in the stored procedure. Having the params allows us to map as many properties to parameters in the stored procedure as we like. If we then loop through all the items in the list first and apply all actions in the actionList per item, we can then call ExecuteScalar on the stored procedure.

foreach (var item in list)
{
    foreach (var action in actionList)
    {
        action.Invoke(this, item);
    }
    var result = sqlCommand.ExecuteScalar();
    sqlCommand.Parameters.Clear();
}

Now, another requirement was to wrap it in a transaction and also to have the verification of the result a bit more flexible. All in all not too complicated, just a matter of introducing another Action:

public ICustomSqlCommandBuilder ExecuteScalarForThisList<T>(
    IList<T> list, 
    Action<object> verify, 
    params Action<ICustomSqlCommandBuilder, T>[] actionList)
{
    sqlCommand.Connection.Open();
    SqlTransaction transaction = sqlCommand.Connection.BeginTransaction();
    sqlCommand.Transaction = transaction;

    try
    {
        foreach (var item in list)
        {
            foreach (var action in actionList)
            {
                action.Invoke(this, item);
            }
            var result = sqlCommand.ExecuteScalar();
            verify(result);
            sqlCommand.Parameters.Clear();
        }
        transaction.Commit();
    }
    catch (SqlException)
    {
        transaction.Rollback();
        throw;
    }
    catch (Exception)
    {
        transaction.Rollback();
        throw;
    }
    return this;
}

Including a bit of exceptionally brittle exception handling and calling the stored procedure on a list of Customers now resolves to:

Action<object> resultConstraint = result =>
{
    if (result != null)
    {
        if ((int)result > 1000)
        {
            throw new Exception("result should be less than 1000!");
        }
    }
};

builder
    .SetStoredProcedureNameTo("sens_sp_modifyCustomerIncome")
    .ExecuteScalarForThisList(
        customerList, 
        resultConstraint,
        (s, t) => s.AddParameterWithValue("id", t.ID),
        (s, t) => s.AddParameterWithValue("income", t.Income)
        //etc for the rest of the properties
    );