C# 仅在需要时有条件地处理 Entity Framework DbContext

Question

我正在努力使我的代码足够智能，以便仅在相关方法的当前执行生命周期内需要时才打开和处理 Entity Framework DBcontext。

基本上，如果将真实上下文传递到方法中，那么我不想处理它。但是，如果它只在相关方法的当前执行生命周期内需要，那么它将在 finally block 中处理

public int UpSertCompanyStockInfo( Guid companyId, string companyName, float stockPrice, float peRatio, CommunicationEngineDatabase context)
{
    bool isContextOnlyCreatedForCurrentMethodExecutionRun = false;
    if (context == null)
    {
        isContextOnlyCreatedForCurrentMethodExecutionRun = true;
        context = new CommunicationEngineDatabase();
    }
    try
    {
        CompanyStockInfo companyStockInfo = new CompanyStockInfo();
        companyStockInfo.CompanyName = companyName;
        companyStockInfo.StockPrice = stockPrice;

        context.CompanyStockInfoTable.Add(companyStockInfo);
        context.SaveChanges();
    }
    catch (Exception _ex)
    {

    }
    finally
    {
        if (isContextOnlyCreatedForCurrentMethodExecutionRun == true && context != null)
        {
            ((IDisposable)context).Dispose();
        }

    }
    return 0;

}

问题是我觉得上述代码的代码行数太多了。有人可以告诉我如何缩短它(甚至可以用 using 语句来做)吗？

Answer 1

你可以将逻辑封装在一个 helper disposable 中(这样你就可以利用 using)类(甚至是 struct)，像这样:

class DbContextScope : IDisposable
{
    public static DbContextScope Open<TContext>(ref TContext context) where TContext : DbContext, new()
        => context != null ? NullScope : new DbContextScope(context = new TContext());
    static readonly DbContextScope NullScope = new DbContextScope(null);
    private DbContextScope(DbContext context) => this.context = context;
    readonly DbContext context;
    public void Dispose() => context?.Dispose();
}

您的样本的用法是:

public int UpSertCompanyStockInfo( Guid companyId, string companyName, float stockPrice, float peRatio, CommunicationEngineDatabase context)
{
    using (DbContextScope.Open(ref context))
    {
        CompanyStockInfo companyStockInfo = new CompanyStockInfo();
        companyStockInfo.CompanyName = companyName;
        companyStockInfo.StockPrice = stockPrice;

        context.CompanyStockInfoTable.Add(companyStockInfo);
        context.SaveChanges();
    }
    return 0;    
}