c# - How to perform an insert and return inserted identity with Dapper?

C# - How to perform an insert and return inserted identity with Dapper?

To perform an insert operation and return the inserted identity value using Dapper in C#, you can use the QueryFirstOrDefault or ExecuteScalar method. Here's how you can do it:

using System.Data.SqlClient; using Dapper; public class UserRepository { private readonly string _connectionString; public UserRepository(string connectionString) { _connectionString = connectionString; } public int InsertUser(User user) { string sql = "INSERT INTO Users (Name, Email) VALUES (@Name, @Email); SELECT SCOPE_IDENTITY();"; using (var connection = new SqlConnection(_connectionString)) { connection.Open(); int userId = connection.QueryFirstOrDefault<int>(sql, user); return userId; } } }

In this code:

  • We define a method InsertUser in the UserRepository class that inserts a User object into the database and returns the inserted identity value.
  • We use Dapper's QueryFirstOrDefault<int> method to execute the SQL statement and return the identity value as an int.
  • The SQL statement includes SELECT SCOPE_IDENTITY();, which retrieves the last inserted identity value within the current scope.

You can use this UserRepository class to insert a user into the database and retrieve the inserted identity value:

var userRepository = new UserRepository("your_connection_string"); User user = new User { Name = "John", Email = "john@example.com" }; int insertedUserId = userRepository.InsertUser(user); Console.WriteLine("Inserted User ID: " + insertedUserId);

Replace "your_connection_string" with your actual database connection string. Also, ensure that the Users table in your database has an identity column for the primary key.

Examples

  1. C# Dapper insert and return identity:

    • Description: This query demonstrates how to perform an INSERT operation and return the inserted identity using Dapper.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public int InsertAndReturnIdentity(string connectionString, string name) { using (var connection = new SqlConnection(connectionString)) { string query = "INSERT INTO Employees (Name) OUTPUT INSERTED.EmployeeID VALUES (@Name)"; return connection.ExecuteScalar<int>(query, new { Name = name }); // Return the inserted identity } }

  2. C# Dapper insert with OUTPUT clause:

    • Description: This query explains how to use the OUTPUT clause to return the inserted identity with Dapper.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public int InsertEmployee(string connectionString, string employeeName) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Employees (Name) OUTPUT INSERTED.EmployeeID VALUES (@Name)"; int insertedId = connection.ExecuteScalar<int>(sql, new { Name = employeeName }); return insertedId; // Return the identity of the newly inserted record } }

  3. C# Dapper insert and retrieve auto-generated key:

    • Description: This query retrieves the auto-generated key (identity) when inserting a record with Dapper.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public int AddProduct(string connectionString, string productName) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Products (ProductName) OUTPUT INSERTED.ProductID VALUES (@ProductName)"; return connection.ExecuteScalar<int>(sql, new { ProductName = productName }); // Retrieve the auto-generated key } }

  4. C# Dapper insert with ExecuteScalar:

    • Description: This query demonstrates using ExecuteScalar to insert a record and return the identity with Dapper.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public int InsertAndGetIdentity(string connectionString, string title) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Books (Title) OUTPUT INSERTED.BookID VALUES (@Title)"; int bookId = connection.ExecuteScalar<int>(sql, new { Title = title }); return bookId; // Get the identity of the inserted record } }

  5. C# Dapper insert with OUTPUT and multiple records:

    • Description: This query demonstrates how to insert multiple records and get their identities using Dapper and the OUTPUT clause.
    • Code Implementation:
      using Dapper; using System.Collections.Generic; using System.Data.SqlClient; public IEnumerable<int> InsertMultipleAndReturnIdentities(string connectionString, IEnumerable<string> names) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Employees (Name) OUTPUT INSERTED.EmployeeID VALUES (@Name)"; var insertedIds = connection.Query<int>(sql, new { Name = names }); // Insert multiple and return identities return insertedIds; } }

  6. C# Dapper insert with returning ID in PostgreSQL:

    • Description: This query shows how to insert a record and return the inserted identity using Dapper with PostgreSQL.
    • Code Implementation:
      using Dapper; using Npgsql; public int InsertAndReturnPostgresIdentity(string connectionString, string customerName) { using (var connection = new NpgsqlConnection(connectionString)) { string sql = "INSERT INTO Customers (Name) RETURNING CustomerID"; // PostgreSQL uses RETURNING return connection.ExecuteScalar<int>(sql, new { Name = customerName }); } }

  7. C# Dapper insert with OUTPUT clause for complex objects:

    • Description: This query demonstrates using the OUTPUT clause to return more complex objects with Dapper.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public class Employee { public int EmployeeID { get; set; } public string Name { get; set; } } public Employee InsertAndReturnEmployee(string connectionString, string employeeName) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Employees (Name) OUTPUT INSERTED.* VALUES (@Name)"; // Return complex object return connection.QuerySingle<Employee>(sql, new { Name = employeeName }); } }

  8. C# Dapper insert with OUTPUT and custom SQL function:

    • Description: This query demonstrates using Dapper with custom SQL functions to return specific data after insert.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public int InsertAndRunCustomFunction(string connectionString, string name) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Users (Name) OUTPUT dbo.CustomFunction(INSERTED.UserID) VALUES (@Name)"; return connection.ExecuteScalar<int>(sql, new { Name = name }); } }

  9. C# Dapper insert with stored procedure returning identity:

    • Description: This query demonstrates how to use a stored procedure with Dapper to insert a record and return its identity.
    • Code Implementation:
      using Dapper; using System.Data; using System.Data.SqlClient; public int InsertUsingStoredProcedure(string connectionString, string productName) { using (var connection = new SqlConnection(connectionString)) { string storedProc = "sp_InsertProduct"; // Example stored procedure var parameters = new DynamicParameters(); parameters.Add("@ProductName", productName); parameters.Add("@ProductID", dbType: DbType.Int32, direction: ParameterDirection.Output); // Output parameter connection.Execute(storedProc, parameters, commandType: CommandType.StoredProcedure); return parameters.Get<int>("@ProductID"); // Return the identity from the output parameter } }

  10. C# Dapper insert with OUTPUT and conditionals:

    • Description: This query demonstrates using the OUTPUT clause with conditional logic to return the identity when certain conditions are met.
    • Code Implementation:
      using Dapper; using System.Data.SqlClient; public int InsertWithConditionalOutput(string connectionString, string name) { using (var connection = new SqlConnection(connectionString)) { string sql = "INSERT INTO Members (Name) OUTPUT INSERTED.MemberID WHERE @Condition = 1 VALUES (@Name)"; return connection.ExecuteScalar<int>(sql, new { Name = name, Condition = 1 }); // Only return if condition is met } }

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