C# SqlKata
last modified July 13, 2023
In this article we show how to program databases in C# with SqlKata library. SqlKata uses SqlBuilder pattern to define queries.
SqlKata is a fluent SQL query builder for C#. It allows us to create SQL statements easily with method chaining.
$ dotnet add project SqlKata $ dotnet add project SqlKata.Execution
We add the SqlKata packages.
$ dotnet add project Npgsql
We add the driver for PostgreSQL database.
CREATE TABLE cars(id serial PRIMARY KEY, name VARCHAR(255), price INT);
INSERT INTO cars(name, price) VALUES('Audi', 52642);
INSERT INTO cars(name, price) VALUES('Mercedes', 57127);
INSERT INTO cars(name, price) VALUES('Skoda', 9000);
INSERT INTO cars(name, price) VALUES('Volvo', 29000);
INSERT INTO cars(name, price) VALUES('Bentley', 350000);
INSERT INTO cars(name, price) VALUES('Citroen', 21000);
INSERT INTO cars(name, price) VALUES('Hummer', 41400);
INSERT INTO cars(name, price) VALUES('Volkswagen', 21600);
In the examples we use this table.
SqlKata query single row
In the first example, we query a single row.
using Npgsql;
using SqlKata.Compilers;
using SqlKata.Execution;
string cs = @"User ID=postgres;Password=passwd;Host=localhost;Database=testdb";
using var con = new NpgsqlConnection(cs);
con.Open();
var compiler = new PostgresCompiler();
var db = new QueryFactory(con, compiler);
var car = db.Query("cars").Where("id", 1).First();
Console.WriteLine(car);
Console.WriteLine($"{car.id} {car.name} {car.price}");
We select the row with Id equal to 1.
string cs = @"User ID=postgres;Password=passwd;Host=localhost;Database=testdb"; using var con = new NpgsqlConnection(cs); con.Open();
First, we define the connection string and open a database connection.
var compiler = new PostgresCompiler(); var db = new QueryFactory(con, compiler);
We choose the compiler for our database and define a QueryFactory.
The QueryFactory is the object that is used to build SQL queries.
var car = db.Query("cars").Where("id", 1).First();
The query is build by chainging three method calls: Query, which
selects the table name, Where, which defines the WHERE SQL clause,
and the First, which returns the first row from the result.
$ dotnet run
{DapperRow, id = '1', name = 'Audi', price = '52642'}
1 Audi 52642
SqlKata fetch all rows
In the next example, we fetch all rows.
using Npgsql;
using SqlKata.Compilers;
using SqlKata.Execution;
string cs = @"User ID=postgres;Password=passwd;Host=localhost;Database=testdb";
using var con = new NpgsqlConnection(cs);
con.Open();
var compiler = new PostgresCompiler();
var db = new QueryFactory(con, compiler);
var cars = db.Query("cars").OrderByDesc("name").Get();
foreach (var car in cars)
{
Console.WriteLine($"{car.id} {car.name} {car.price}");
}
The program takes all rows from the table and orders the output by name in descending order.
var cars = db.Query("cars").OrderByDesc("name").Get();
We get the result by chaining Query, OrderByDesc,
and Get calls.
$ dotnet run 4 Volvo 29000 8 Volkswagen 21600 3 Skoda 9000 2 Mercedes 57127 7 Hummer 41400 6 Citroen 21000 5 Bentley 350000 1 Audi 52642
SqlKata insert row
In the next example, we insert a new row into the table.
using Npgsql;
using SqlKata.Compilers;
using SqlKata.Execution;
string cs = @"User ID=postgres;Password=passwd;Host=localhost;Database=testdb";
using var con = new NpgsqlConnection(cs);
con.Open();
var compiler = new PostgresCompiler();
var db = new QueryFactory(con, compiler);
int n = db.Query("cars").Insert(new
{
name = "Toyota",
price = 27890
});
if (n == 1)
{
Console.WriteLine("New row inserted");
}
The Insert method is used to generate an INSERT SQL statement.
SqlKata delete row
In the next example, we delete a row from the table.
using Npgsql;
using SqlKata.Compilers;
using SqlKata.Execution;
string cs = @"User ID=postgres;Password=passwd;Host=localhost;Database=testdb";
using var con = new NpgsqlConnection(cs);
con.Open();
var compiler = new PostgresCompiler();
var db = new QueryFactory(con, compiler);
int id = 9;
int n = db.Query("cars").Where("id", id).Delete();
if (n == 1)
{
Console.WriteLine("row succesfully deleted");
}
The program deletes a row with id equal to 9.
int n = db.Query("cars").Where("id", id).Delete();
To create the statement, we used the Query, Where,
and Delete method calls.
SQL Server example
We have worked with PostgreSQL database. The next example shows how to create a simple example for SQL Server.
$ dotnet add package SqlKata $ dotnet add package SqlKata.Execution $ dotnet add package System.Data.SqlClient
We add these three packages to our project.
DROP TABLE IF EXISTS cars;
CREATE TABLE cars(id INT PRIMARY KEY IDENTITY(1, 1), name VARCHAR(255), price INT);
INSERT INTO cars(name, price) VALUES('Audi',52642);
INSERT INTO cars(name, price) VALUES('Mercedes',57127);
INSERT INTO cars(name, price) VALUES('Skoda',9000);
INSERT INTO cars(name, price) VALUES('Volvo',29000);
INSERT INTO cars(name, price) VALUES('Bentley',350000);
INSERT INTO cars(name, price) VALUES('Citroen',21000);
INSERT INTO cars(name, price) VALUES('Hummer',41400);
INSERT INTO cars(name, price) VALUES('Volkswagen',21600);
We have the SQL for the SQL Server.
using System.Data.SqlClient;
using SqlKata.Compilers;
using SqlKata.Execution;
string cs = @"Server=localhost\SQLEXPRESS;Database=testdb;Trusted_Connection=True;";
using var con = new SqlConnection(cs);
con.Open();
var compiler = new SqlServerCompiler();
var db = new QueryFactory(con, compiler);
var cars = db.Query("cars").Get<Car>();
foreach (var car in cars)
{
Console.WriteLine(car);
}
class Car
{
public int Id { get; init; }
public string Name { get; init; }
public int Price { get; init; }
public Car(int Id, string Name, int Price)
{
this.Id = Id;
this.Name = Name;
this.Price = Price;
}
public override string ToString()
{
return $"[{this.Id} {this.Name} {this.Price}]";
}
}
In the example, we fetch all the rows from the table of an SQL Server database.
using System.Data.SqlClient;
The namespace is built into the .NET Core.
using var con = new SqlConnection(cs);
We use SqlConnection.
var compiler = new SqlServerCompiler();
We use SqlServerCompiler.
Source
In this article we have shown how to program databases in C# with SqlKata.
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