Partial Type Inference in .Net

When designing fluent APIs, one issue that comes up is partial type inference.  If a method has two type parameters, there is no way to call it and only specify one of the type parameters (and leave the other inferred by the compiler)

For example, suppose we are creating a type-safe wrapper around a parameterized SqlCommand.
Ideally, it would be called like this:

using(DbConnection connection = ...) {
    var result = connection.ExecuteScalar<int>(
        "SELECT COUNT(*) FROM TableName WHERE Modified > someDate",
        new { someDate }

Where the generic parameter specifies the return type.

In order to implement this efficiently, one would create methods at runtime which add DbParameters for each property in the anonymous type, and store them in a static generic class.   
It would look something like this:

static class Extensions {
    public static void AddParams<TParam>(this IDbCommand command, 
                                         TParam parameters)
        where TParam : class { 
        if (parameters != null) 
            ParamAdders<TParam>.Adder(command, parameters);
    static class ParamAdders<TParam> where TParam : class {
        public delegate void ParamAdder(IDbCommand command,
                                        TParam parameters);
        public static readonly ParamAdder Adder = CreateParamAdder();

        private static ParamAdder CreateParamAdder() { 
            return ...; 

However, that requires that the ExecuteScalar extension method take TParam as a generic parameter.  Since anonymous types can only be passed as generic parameters via type inference, this makes it impossible to pass the return type as a generic parameter.

To fix this issue, we can split the generic parameters across two methods.  We can change the extension method to take a single generic parameter, and return a generic class with a method that takes the other generic parameter.

For example:

static class BetterExtensions {
    public static SqlStatement<T> Sql<T>(this IDbConnection conn,
                                         string sqlText) { 
        return new SqlStatement<T>(conn, sqlText); 
class SqlStatement<TReturn> : IHideObjectMembers {
    public SqlStatement(IDbConnection connection, string sql) { 
        Connection = connection; 
        Sql = sql;
    public IDbConnection Connection { get; private set; }
    public string Sql { get; private set; }

    public TReturn Execute() { return Execute<object>(null); }
    public TReturn Execute<TParam>(TParam parameters)
         where TParam : class {
        return ...;

I use an IHideObjectMembers interface to hide the methods inherited from Object from IntelliSense.  Note that the interface must be defined in an assembly outside of your solution. (or, to be more precise, that isn’t a Project reference)

This version would be called like this:

using(IDbConnection connection = null) {
    var result = connection.Sql<int>(
        "SELECT COUNT(*) FROM TableName WHERE Modified > someDate"
    ).Execute(new { someDate });

The return type is specified explicitly in the call to Sql<T>(), and the parameter type is passed implicitly to Execute<TParam>().


It's worth taking a longer look at this article. Tracey

I advise you to check this out if you want to read college essay examples. I had such experience recently, by the way

This is such an extraordinary asset, to the point that you are giving and you give it away for nothing. I adore seeing blog that comprehend the quality. Im happy to have discovered this post as its such a fascinating one! I am dependably watchful for quality posts and articles so i assume im fortunate to have discovered this!
Play now friv games for free!

Instructional exercise is simply awesome..It is truly useful for a novice like me.. I am a standard adherent of your blog. Actually quite educational post you shared here. Domyassignmentforme

At present, in a conjuring of a conventional technique, you either need to indicate the entirety of the sort contentions or none of them, in the last case contingent upon the compiler to gather them for you. Do My Assignment For Me

Your recommendations really work in practice. I am currently working on an literary analysis essay and actively using this advice. I hope others will also take advantage of this opportunity.

The upsides of utilizing the organizer board are likewise talked about in this article, for which the expense of introducing this framework is legitimized for an energetic angler. top cleaning companies in dubai

<a href=">residential building design and construction - heritagedesignbuildgroup</a> is the most potential service given by heritage group with most excellence.

Partial Type Inference in .Net is a standout amongst other blog that I have at any point seen so far go here Write My Assignment UK for subtleties.

Thank you for sharing good content. I found your blog on google search it’s very helpful for me.

I'm almost certain there was an issue in regards to recursive conventional, yet I can't track down it. Without recursive kind boundaries, I think 2 is better in light of the fact that is less verbose, since verbosity is important for the issue here leather jacket for sale. Be that as it may, with recursive sort boundaries, I figure 1 would fit better.

Develops a sort comprising of all properties of Best Graphic Illustrators Type set to required. Something contrary to Partial.,Constructs a sort with all properties of Type set to readonly, which means the properties of the built kind can't be reassigned.

Sweet blog! I found it while browsing on Yahoo News. Do you have any tips on how to get listed in Yahoo News? do my college homework I’ve been trying for a while but I never seem to get there! Thank you

to the point that you are giving and you give it away for nothing. extraordinary asset, UK's Top-Rated and Students' Most Favorite Assignment Writing services uk is Here to Offer Expert Help in Most Affordable Prices with a Guarantee to an A or A+ Grade
Assignment writing services UK

have well-qualified writers to write different types of academic papers. Buy Assignments Online We accept requests for essays, dissertations, course research papers, and term papers

Thanks for sharing the piece of code. It was very helpful for me in my final year project. Keep this work up and share more tips. Now it's time to avail Embroidered T Shirts for more information.

This is such an extraordinary blog, to the point that you are giving and you give it away for nothing. I adore seeing blog that comprehend the quality. I am happy to have discovered this post as its such a fascinating one! Thank you for sharing good content. I found your blog on google search it’s very helpful for me.
can a protection order be dropped in virginia

Your solution elegantly resolves the issue of partial type inference in fluent APIs, making the code cleaner and more intuitive. The use of the IHideObjectMembers interface is a clever touch to improve IntelliSense readability. Prevención Violencia Doméstica Acto Nueva Jersey

Brilliant solution to the challenge of partial type inference in .NET! The use of a fluent API with split generic parameters elegantly addresses the issue, offering a clean and efficient approach to designing type-safe wrappers for SqlCommands.
New York Divorce Law Alimony

pgslot เว็บตรง เกมส์สล็อตออนไลน์ เกมยอดนิยมจากผู้เล่นทั้งโลกตอนนี้ การเล่นสล็อตของคุณจะไม่มีเบื่ออีกต่อไป pg slot ขอแนะนำให้มาเล่นกับเว็บเรามีทางเลือกทั้งเกมเเละโปรโมชั่น

Post a Comment