如何基于参数为方法设置不同入口点以遵循DRY原则

问题背景 #

我有一个SetDisplayCollection方法，无需每次运行全部代码，希望根据场景仅执行部分代码。为遵循DRY（Don't Repeat Yourself）原则，如何基于传入参数为该方法设置不同的执行入口？

原代码示例：

public void SetDisplayCollection(string input)
{
    //SWITCH:
    //Input 1 entry Point
    ChosenSite = SiteCollection.Where(x => x.Guid == chosenConcept.SiteGuid && x.Name == chosenConcept.SiteName).FirstOrDefault();
    //Input 2 entry point
    BuildingDisplayCollection = new ObservableCollection<BuildingConcept>(BuildingCollection.Where(x => x.RelatingName == ChosenSite.Name).ToList());
    ChosenBuilding = BuildingDisplayCollection.Where(x => x.Guid == chosenConcept.BuildingGuid && x.Name == chosenConcept.BuildingName).FirstOrDefault();
    //Input 3 entry point
    BuildingStoreyDisplayCollection = new ObservableCollection<BuildingStoreyConcept>(BuildingStoreyCollection.Where(x => x.RelatingName == ChosenBuilding.Name).ToList());
    ChosenBuildingStorey = BuildingStoreyDisplayCollection.Where(x => x.Name == chosenConcept.BuildingStoreyName).FirstOrDefault();
    //default no entry
}

期望的三种执行场景：

• 运行全部代码
• 运行后2/3代码（跳过开头部分）
• 运行最后1/3代码（跳过前2/3部分）

解决方案：拆分逻辑+参数驱动执行 #

核心思路是把原方法里的三个独立逻辑块拆成单独的私有方法，通过传入的参数决定调用哪些方法，既避免重复代码，又能灵活控制执行流程。

步骤1：拆分独立逻辑块

把每个执行段封装成单一职责的私有方法，确保每个逻辑只写一次：

private void LoadChosenSite()
{
    ChosenSite = SiteCollection.Where(x => x.Guid == chosenConcept.SiteGuid && x.Name == chosenConcept.SiteName).FirstOrDefault();
}

private void LoadBuildingCollections()
{
    BuildingDisplayCollection = new ObservableCollection<BuildingConcept>(BuildingCollection.Where(x => x.RelatingName == ChosenSite.Name).ToList());
    ChosenBuilding = BuildingDisplayCollection.Where(x => x.Guid == chosenConcept.BuildingGuid && x.Name == chosenConcept.BuildingName).FirstOrDefault();
}

private void LoadBuildingStoreyCollections()
{
    BuildingStoreyDisplayCollection = new ObservableCollection<BuildingStoreyConcept>(BuildingStoreyCollection.Where(x => x.RelatingName == ChosenBuilding.Name).ToList());
    ChosenBuildingStorey = BuildingStoreyDisplayCollection.Where(x => x.Name == chosenConcept.BuildingStoreyName).FirstOrDefault();
}

步骤2：重构SetDisplayCollection方法，根据参数控制执行

用参数判断要执行的逻辑组合，示例先用字符串匹配，后续可以优化为枚举：

public void SetDisplayCollection(string input)
{
    switch(input)
    {
        case "Full": // 运行全部代码
            LoadChosenSite();
            LoadBuildingCollections();
            LoadBuildingStoreyCollections();
            break;
        case "BuildingOnly": // 运行后2/3代码
            LoadBuildingCollections();
            LoadBuildingStoreyCollections();
            break;
        case "StoreyOnly": // 运行最后1/3代码
            LoadBuildingStoreyCollections();
            break;
        default: // 默认不执行任何逻辑
            break;
    }
}

优化建议：用枚举替代字符串参数

为了避免字符串拼写错误，建议定义枚举规范输入参数：

public enum ExecutionScope
{
    Full,
    BuildingOnly,
    StoreyOnly,
    None
}

public void SetDisplayCollection(ExecutionScope scope)
{
    switch(scope)
    {
        case ExecutionScope.Full:
            LoadChosenSite();
            LoadBuildingCollections();
            LoadBuildingStoreyCollections();
            break;
        case ExecutionScope.BuildingOnly:
            LoadBuildingCollections();
            LoadBuildingStoreyCollections();
            break;
        case ExecutionScope.StoreyOnly:
            LoadBuildingStoreyCollections();
            break;
        default:
            break;
    }
}

为什么符合DRY原则？ #

每个业务逻辑块（加载站点、加载建筑、加载楼层）只实现一次，不同场景只是组合调用这些方法，没有重复代码。后续如果需要修改某段逻辑，只需要修改对应的私有方法即可，所有调用该逻辑的场景都会同步更新。

内容的提问来源于stack exchange，提问作者Ryan Daley