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有什么方法可以使这两个块具有共同的功能吗

refactoring .net-core generics c#

Glory Raj · 技术社区 · 2 年前

我有两个街区;在每个块中,我使用命令和读取器从表中检索数据,转换数据,然后更新数据。我希望通过将表名、类型和转换函数从这两个块传递给该函数来提取公共函数

下面是相同的代码,

//块#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();

//块#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();

我不能合并 OldSteamSystem 和 OldFuelSystem

那么,有谁能告诉我如何用它来实现一个公共函数吗?

1 回复 | 直到 2 年前

gunr2171 2 年前

使用泛型,询问表名和转换对象的方法。

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 不同的 键入,然后将方法签名更改为

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