Introduction To Dapper Generic Repository

Dapper is a micro ORM product for Microsoft .NET Framework. It provides a set of actions for mapping POCO objects to Relational databases.with adequate performance.

Dapper is open-source and has Apache License 2.0 or the MIT License and is easily installable by NuGet.

Index

Dapper features
Database for the Test Project
La clase DPGenericRepository
Create DPGenericRepository object
Methods descriptions
- All / AllAsync
- GetData(object parameters) / GetDataAsync
- GetData(string qry, object parameters) / GetDataAsync
- Find(object pks) / FindAsync
- Add(TEntity entity) / AddAsync
- Remove(object pk) / RemoveAsync
- Update(TEntity entity, object pk) / RemoveAsync
- InsertOrUpdate(TEntity entity, object pk) / RemoveAsync

Dapper features

Its main advantages as compared with other ORMs are given below.

Performance is faster ORM in .NET.
Few lines of code.
Object Mapper.
Choice of static/dynamic object binding.
Easy handling of SQL query.
Multiple query support.
Support and easy handling of the stored procedures.
Operating directly on IDBConnection class.
Bulk data insert functionality.

Data from Wikipedia.

The biggest disadvantage of this wonderful ORM is the return to queries in strings because it is less useful and we lose the syntactic errors in compilation time.

I have created a Generic Repository based in Dapper, approaching its philosophy to Entity Framework, removing the string queries as far as possible, primarily for delete, update, insert, and for all method's queries.

I tried to create a custom library with the comfort of Entity Framework and with the performance of Dapper.

I have tested DPGenericRepository with Sql Server and Oracle, but it must be compatible with all databases that are Dapper supported.

I have other genericRepositories libraries of Entity Framework and EntityFramework+Dapper, and if my time allows, I will explain it in other articles. These libraries are compatible with each, and they will be easily replaced.

This project is open source and it is available in GitHub.

We can install through NuGet,

Database for the Test Project

Proceed, as shown below.

It has two tables given below.

DPGenericRepository Class

DPGenericRepository is a principal class of MoralesLarios.Data.Dapper namespace. It has the functionality to create and transform our classes in GenericRepositories for Dapper.

The next image shows the principal class for this article DPGenericRepository and then implements the interfaces. We can see the other generics repositories EFGenericRepository and MLGenericRepository, which will be visible in the deliveries given below with your compatibilities.

IGenericRepository Interface

public interface IGenericRepository<TEntity> : IDisposable where TEntity : class
{
IEnumerable<TEntity> All();
Task<IEnumerable<TEntity>> AllAsync();
IEnumerable<TEntity> GetData(string qry, object parameters);
Task<IEnumerable<TEntity>> GetDataAsync(string qry, object parameters);
TEntity Find(object pksFields);
Task<TEntity> FindAsync(object pksFields);
int Add(TEntity entity);
Task<int> AddAsync(TEntity entity);
int Add(IEnumerable<TEntity> entities);
Task<int> AddAsync(IEnumerable<TEntity> entities);
void Remove(object key);
Task RemoveAsync(object key);
int Update(TEntity entity, object pks);
Task<int> UpdateAsync(TEntity entity, object pks);
int InstertOrUpdate(TEntity entity, object pks);
Task<int> InstertOrUpdateAsync(TEntity entity, object pks);
}

IDPGenericRepository Interface

public interface IDPGenericRepository<TEntity> : IGenericRepository<TEntity> where TEntity : class
{
IEnumerable<TEntity> GetData(object filter);
Task<IEnumerable<TEntity>> GetDataAsync(object filter);
}

DPGenericRepository implements the IDPGenericRepository, which in turn implements IGenericRepository for compatibility with other Generic Repositories of the library.

DPGenericRepository contains a set of the regular use of methods in the database, but we can extend your functionality through inheritance.

Creating a DPGenericRepository Object

Dapper is based on an extension class for the IDbConnection interface, therefore DPGenericRepository needs an object IDbConnection injected in your constructor.

We can create a DPGenericRepository in two different ways, which are given below.

Directly in code

using (var conn = new SqlConnection(cs))
{
var departmentRepository = new DPGenericRepository<Departments>(conn);
// inject IDbConnection
}

We can use a second constructor with a new char parameter. This new parameter ‘parameterIdentified’ shows the char SQL parameter indicator. ‘@’ for default, gives compatibility with SQL Server, for Oracle we use ‘:’.

Example for Oracle

using (var conn = new SqlConnection(cs))
{
var departmentRepository = new DPGenericRepository<Departments>(conn, parameterIdentified:':'
);
// inject IDbConnection
}

For Inheritance

public class DepartmentRepository : DPGenericRepository<Departments>
{
public DepartmentRepository(IDbConnection conn, char parameterIdentified = '@') : base(conn, parameterIdentified)
{
}
}

Change the default value parameterIdentified to ‘:’ for Oracle.

public class DepartmentRepository : DPGenericRepository<Departments>
{
public DepartmentRepository(IDbConnection conn, char parameterIdentified = ':') : base(conn, parameterIdentified)
{
}
}

Methods Descriptions

Let’s try to explain all DPGenericRepository methods with an example for each one.

Note

It’s important to point out that any method takes an object parameter with ‘pk’ or ‘parameters’ definitions. These methods create an anonymous type with an alias type equals to the relational type in the POCO object.

Let’s see your methods:

All / AllAsync

The All method obtains all the data of the table.

var departmentRepository = new DPGenericRepository<Departments>(conn);
var allDepartments = departmentRepository.All();

GetData(object parameters) / GetDataAsync

GetData method with one parameter has built a query for Dapper with an equals sequences of ‘ands’ for parameter value.

var employeesRepository = new DPGenericRepository<Employees>(conn);
object parameters = new { Name = "Peter", Age = 30, Incomes = 35000 };
var employeesPeter30years35000Incomes = employeesRepository.GetData(parameters);
// ** This is the automatic query value **
// "SELECT * FROM EMPLOYEES " +
// " WHERE NAME = @Name " +
// " AND AGE = @Age " +
// " AND INCOMES = @Incomes";

GetData(string qry, object parameters) / GetDataAsync

GetData method with two parameters, is a method with less automation, because it isn’t possible to infer data and your execution is practically equal with a normal query Dapper execute.

var employeesRepository = new DPGenericRepository<Employees>(conn);
string qry = "SELECT * FROM EMPLOYEES WHERE AGE > @Age AND INCOMES > @Incomes";
object parameters = new { Age = 30, Incomes = 35000 };
var employeesMore30yearsMore35000 = employeesRepository.GetData(qry, parameters);

Find(object pks) / FindAsync

Find method is very similar to GetData (object paramaters). This signature exists for down compatibility with Entity Framework GenericRepository, in which it has a sense for its architecture. The parameter pks, would be the pks properties in the table ordered.

var employeesRepository = new DPGenericRepository<Employees>(conn);
object pk = new { EmployeeID = 3 };
var employee3 = employeesRepository.Find(pk);

Add(TEntity entity) / AddAsync

Add an entity in the Database.

var employeesRepository = new DPGenericRepository<Employees>(conn);
var newEmployee = new Employees
{
Name = "Lucas",
Age = 19,
Incomes = 15000,
DepartmentID = 3,
EntryDate = DateTime.Today
};
var rowsInserted = employeesRepository.Add(newEmployee);

Add(IEnumerable<TEntity> entities) / AddAsync

Insert a set of entities in the Database. For the Dapper versatility, this insertion is carried through bulk copy. Is a much faster process.

var employeesRepository = new DPGenericRepository<Employees>(conn);
var newEmployees = new List<Employees>()
{
new Employees
{
Name = "Lucas",
Age = 19,
Incomes = 15000,
DepartmentID = 3,
EntryDate = DateTime.Today
},
new Employees
{
Name = "Edgar",
Age = 64,
Incomes = 100000,
DepartmentID = 3,
EntryDate = DateTime.Today
}
};
var rowsInserted = employeesRepository.Add(newEmployees);

Remove(object pk) / RemoveAsync

Remove a row of the database from pk.

var employeesRepository = new DPGenericRepository<Employees>(conn);
object pk = new { EmployeeID = 5 };
employeesRepository.Remove(pk);

Update(TEntity entity, object pk) / RemoveAsync

Update the row in the database from pk.

var employeesRepository = new DPGenericRepository<Employees>(conn);
object pk = new { EmployeeID = 1 };
var employeeOne = employeesRepository.Find(pk);
employeeOne.DepartmentID = 2;
employeeOne.Incomes = 300000;
employeesRepository.Update(employeeOne, pk);

InsertOrUpdate(TEntity entity, object pk) / RemoveAsync

This method checks if an entity exists in the database through its pk. If a row exists, update its value, and if it doesn’t exist insert the entity in the database.

It is practical with a typical screen for insert/update values because we can reuse the code.

var employeesRepository = new DPGenericRepository<Employees>(conn);
var employee = myFile.GetEmployee();
var pk = new { employee.EmployeeID };
/// we don't know if employee exists
/// InsertOrUpdate method be responsible for INSERT OR UPDATE
employeesRepository.InstertOrUpdate(employee, pk);

You can test all methods in the Test Project.

5 Comments

Join the conversation! Your thoughts help the community grow.

Supun Silva4y ago
Can we use another table name by specifying the Table attribute [Table("tbl_Author")] and also for column names? Please refer to Dapper Contrib data annotation
Al Junior5y ago
Hi, thank you for this post:can your implementation handle getting nested objects?
vinay khanna5y ago
I need the source of the generic repository
Juan Francisco Morales Larios9y ago
Hi parminder, my base class doesn't covered store procedure, but you extend your Dapper repository with your methods with stores procedures call. I put you the information of dapper, find sotre procedure section. https://github.com/StackExchange/Dapper
Parminder Pal Singh9y ago
I need to call the stored procedure and get output from it, how can i do with dapper ?