有什么辦法可以使這兩個塊的通用功能

Question

我有兩個街區； 在每個塊中，我使用命令和閱讀器從表中檢索數據並轉換數據，然后更新相同的數據。 我希望通過將表名、類型和轉換函數從這兩個塊傳遞給該函數來提取通用函數

下面是相同的代碼，

// 塊 #1

using var queryProjectSteamSystemsCommand = dbContext.Database.GetDbConnection().CreateCommand();
queryProjectSteamSystemsCommand.CommandText = @"SELECT ""Id""::varchar, ""InitialObject""::varchar from ""DesignHubProjectSteamSystems""";
using var steamSystemProjectsReader = queryProjectSteamSystemsCommand.ExecuteReader();

if (steamSystemProjectsReader.HasRows)
{
    while (steamSystemProjectsReader.Read())
    {
        var id = steamSystemProjectsReader.IsDBNull(0) ? Guid.Empty : Guid.Parse(steamSystemProjectsReader.GetString(0));
        var steamSystemJson = steamSystemProjectsReader.IsDBNull(1) ? "null" : steamSystemProjectsReader.GetString(1);
        var projSteamSystemInitialObj = JsonConvert.DeserializeObject<OldSteamSystem>(steamSystemJson);
        string json = JsonConvert.SerializeObject(TransformProjectSteamSystem(projSteamSystemInitialObj)).Replace("'", "''", StringComparison.Ordinal);
        migrationBuilder.Sql($"UPDATE \"DesignHubProjectSteamSystems\"  SET \"InitialObject\" = '{json}'::jsonb WHERE \"Id\" = '{id}'");
    }
}
steamSystemProjectsReader.Close();

// 塊 #2

using var queryProjectFuelSystemsCommand = dbContext.Database.GetDbConnection().CreateCommand();
queryProjectFuelSystemsCommand.CommandText = @"SELECT ""Id""::varchar, ""InitialObject""::varchar from ""DesignHubProjectFuelSystems""";
using var fuelSystemProjectsReader = queryProjectFuelSystemsCommand.ExecuteReader();

if (fuelSystemProjectsReader.HasRows)
{
    while (fuelSystemProjectsReader.Read())
    {
        var id = fuelSystemProjectsReader.IsDBNull(0) ? Guid.Empty : Guid.Parse(fuelSystemProjectsReader.GetString(0));
        var fuelSystemJson = fuelSystemProjectsReader.IsDBNull(1) ? "null" : fuelSystemProjectsReader.GetString(1);
        var projFuelSystemInitialObj = JsonConvert.DeserializeObject<OldFuelSystem>(fuelSystemJson);

        string json = JsonConvert.SerializeObject(TransformProjectFuelSystem(projFuelSystemInitialObj)).Replace("'", "''", StringComparison.Ordinal);
        migrationBuilder.Sql($"UPDATE \"DesignHubProjectFuelSystems\"  SET \"InitialObject\" = '{json}'::jsonb WHERE \"Id\" = '{id}'");
    }
}
fuelSystemProjectsReader.Close();

我不能將OldSteamSystem和OldFuelSystem兩個不同的類結合起來。 我無法從這兩者中制作任何熟悉的接口和抽象類。

那么，任何人都可以讓我知道如何使用它來制作一個通用功能嗎？

提前謝謝了！！！

Answer 1

使用泛型，並詢問表名和轉換對象的方法。

void DoTheThing<TSystem>(string tableName, Func<TSystem, TSystem> transform)
{
    using var command = dbContext.Database.GetDbConnection().CreateCommand();
    command.CommandText = @$"SELECT ""Id""::varchar, ""InitialObject""::varchar from ""{tableName}""";
    // I know I complain about SQL injection, you get to fix this one...

    using var reader = command.ExecuteReader();

    if (reader.HasRows)
    {
        while (reader.Read())
        {
            var id = reader.IsDBNull(0) ? Guid.Empty : Guid.Parse(reader.GetString(0));
            var initialJson = reader.IsDBNull(1) ? "null" : reader.GetString(1);
            var initialObj = JsonConvert.DeserializeObject<TSystem>(initialJson);
            
            // this uses the "transform" parameter, IE a method your caller provides
            string transformedJson = JsonConvert.SerializeObject(transform(initialObj)).Replace("'", "''", StringComparison.Ordinal);
            migrationBuilder.Sql($"UPDATE \"{tableName}\"  SET \"InitialObject\" = '{transformedJson}'::jsonb WHERE \"Id\" = '{id}'");
            // again, SQL injection
        }
    }

    reader.Close();
}

如果transform方法采用一種類型並返回另一種類型，則將方法簽名更改為

void DoTheThing<TSystem, TTransformed>(string tableName, Func<TSystem, TTransformed> transform)