Add project files.

OfflineDemoApi/Data/SqlDataAccess.cs

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+using Dapper;
+using Microsoft.Data.SqlClient;
+using System.Data;
+
+namespace OfflineDemoApi.Data;
+
+public class SqlDataAccess : ISqlDataAccess
+{
+	private readonly IConfiguration _config;
+
+	public SqlDataAccess(IConfiguration config)
+	{
+		_config = config;
+	}
+
+	public async Task<List<T>> LoadData<T, U>(string storedProcedure,
+											  U parameters,
+											  string connectionStringName)
+	{
+		string connectionString = _config.GetConnectionString(connectionStringName) ??
+			throw new KeyNotFoundException("Did not find the connection string specified");
+
+		using IDbConnection connection = new SqlConnection(connectionString);
+
+		List<T> output = (await connection.QueryAsync<T>(
+			storedProcedure,
+			parameters,
+			commandType: CommandType.StoredProcedure)).ToList();
+
+		return output;
+	}
+
+	public async Task<T> SaveDataScalar<T, U>(string storedProcedure,
+										   U parameters,
+										   string connectionStringName)
+	{
+		string connectionString = _config.GetConnectionString(connectionStringName) ??
+			throw new KeyNotFoundException("Did not find the connection string specified");
+
+		using IDbConnection connection = new SqlConnection(connectionString);
+
+		T? output = await connection.ExecuteScalarAsync<T>(storedProcedure, parameters, commandType: CommandType.StoredProcedure);
+
+		return output ?? throw new ArgumentNullException("The return value was null, which is an invalid result.");
+	}
+
+	public async Task SaveData<T>(string storedProcedure,
+								  T parameters,
+								  string connectionStringName)
+	{
+		string connectionString = _config.GetConnectionString(connectionStringName) ??
+			throw new KeyNotFoundException("Did not find the connection string specified");
+
+		using IDbConnection connection = new SqlConnection(connectionString);
+
+		await connection.ExecuteAsync(storedProcedure, parameters, commandType: CommandType.StoredProcedure);
+	}
+}