first commit

RS_system/Data/PostgresQueryExecutor.cs

@@ -0,0 +1,39 @@
+using System.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Storage;
+using Npgsql;
+
+namespace Rs_system.Data;
+
+public static class PostgresQueryExecutor
+{
+    public static async Task<List<T>> ExecuteQueryAsync<T>(
+        DbContext context,
+        string sql,
+        Func<NpgsqlDataReader, T> map,
+        Action<NpgsqlParameterCollection>? parameters = null
+    )
+    {
+        var conn = (NpgsqlConnection)context.Database.GetDbConnection();
+
+        if (conn.State != ConnectionState.Open)
+            await conn.OpenAsync();
+
+        await using var cmd = new NpgsqlCommand(sql, conn);
+
+        var currentTx = context.Database.CurrentTransaction;
+        if (currentTx != null)
+            cmd.Transaction = (NpgsqlTransaction)currentTx.GetDbTransaction();
+
+        parameters?.Invoke(cmd.Parameters);
+
+        var results = new List<T>();
+        await using var reader = await cmd.ExecuteReaderAsync();
+        while (await reader.ReadAsync())
+        {
+            results.Add(map(reader));
+        }
+
+        return results;
+    }
+}