Dapper - a simple object mapper for .Net
Located at https://github.com/DapperLib/Dapper/releases
MyGet Pre-release feed: https://www.myget.org/gallery/dapper
Package NuGet Stable NuGet Pre-release Downloads MyGet Dapper Dapper.EntityFramework Dapper.EntityFramework.StrongName Dapper.Rainbow Dapper.SqlBuilder Dapper.StrongNamePackage Purposes:
Dapper was originally developed for and by Stack Overflow, but is F/OSS. Sponsorship is welcome and invited - see the sponsor link at the top of the page. A huge thanks to everyone (individuals or organisations) who have sponsored Dapper, but a massive thanks in particular to:
Dapper is a NuGet library that you can add in to your project that will enhance your ADO.NET connections via
extension methods on your DbConnection instance. This provides a simple and efficient API for invoking SQL, with support for both synchronous and
asynchronous data access, and allows both buffered and non-buffered queries.
It provides multiple helpers, but the key APIs are:
// insert/update/delete etc
var count = connection.Execute(sql [, args]);
// multi-row query
IEnumerable<T> rows = connection.Query<T>(sql [, args]);
// single-row query ({Single|First}[OrDefault])
T row = connection.QuerySingle<T>(sql [, args]);
where args can be (among other things):
Dictionary<string,object>DynamicParameters instancepublic class Dog
{
public int? Age { get; set; }
public Guid Id { get; set; }
public string Name { get; set; }
public float? Weight { get; set; }
public int IgnoredProperty { get { return 1; } }
}
var guid = Guid.NewGuid();
var dog = connection.Query<Dog>("select Age = @Age, Id = @Id", new { Age = (int?)null, Id = guid });
Assert.Equal(1,dog.Count());
Assert.Null(dog.First().Age);
Assert.Equal(guid, dog.First().Id);
This method will execute SQL and return a dynamic list.
Example usage:
var rows = connection.Query("select 1 A, 2 B union all select 3, 4").AsList();
Assert.Equal(1, (int)rows[0].A);
Assert.Equal(2, (int)rows[0].B);
Assert.Equal(3, (int)rows[1].A);
Assert.Equal(4, (int)rows[1].B);
Example usage:
var count = connection.Execute(@"
set nocount on
create table #t(i int)
set nocount off
insert #t
select @a a union all select @b
set nocount on
drop table #t", new {a=1, b=2 });
Assert.Equal(2, count);
The same signature also allows you to conveniently and efficiently execute a command multiple times (for example to bulk-load data)
Example usage:
var count = connection.Execute(@"insert MyTable(colA, colB) values (@a, @b)",
new[] { new { a=1, b=1 }, new { a=2, b=2 }, new { a=3, b=3 } }
);
Assert.Equal(3, count); // 3 rows inserted: "1,1", "2,2" and "3,3"
Another example usage when you already have an existing collection:
var foos = new List<Foo>
{
{ new Foo { A = 1, B = 1 } }
{ new Foo { A = 2, B = 2 } }
{ new Foo { A = 3, B = 3 } }
};
var count = connection.Execute(@"insert MyTable(colA, colB) values (@a, @b)", foos);
Assert.Equal(foos.Count, count);
This works for any parameter that implements IEnumerable<T> for some T.
A key feature of Dapper is performance. The following metrics show how long it takes to execute a SELECT statement against a DB (in various config, each labeled) and map the data returned to objects.
The benchmarks can be found in Dapper.Tests.Performance (contributions welcome!) and can be run via:
dotnet run --project .\benchmarks\Dapper.Tests.Performance\ -c Release -f net8.0 -- -f * --join
Output from the latest run is:
BenchmarkDotNet v0.13.7, Windows 10 (10.0.19045.3693/22H2/2022Update)
Intel Core i7-3630QM CPU 2.40GHz (Ivy Bridge), 1 CPU, 8 logical and 4 physical cores
.NET SDK 8.0.100
[Host] : .NET 8.0.0 (8.0.23.53103), X64 RyuJIT AVX
ShortRun : .NET 8.0.0 (8.0.23.53103), X64 RyuJIT AVX