当一个方法调用另一个方法并且都使用DbContext时，处理DbContext的正确方法

您可能希望将表删除逻辑移动到单独的方法中，并从DeleteChain和deleetesheet中调用它，如下所示:

public class ControllerHelper
{
    public void DeleteChain(int? chainId) {
        using (var db = new UranusContext()) {
            var chain = db.Chains.Include(c => c.Sheets)
                .SingleOrDefault(c => c.ChainId == chainId);
            // Removes sheets (children)
            foreach (var sheet in chain.Sheets.ToList()) {
                DeleteSheet(db, sheet);
            }
            db.Chains.Remove(chain);
            db.SaveChanges();
        }
    }
    public void DeleteSheet(int? sheetId) {
        using (var db = new UranusContext()) {
            var sheet = db.Sheets.Include(s => s.FileDetails)
                .Include(s => s.SheetsCounties)
                .SingleOrDefault(s => s.SheetId == sheetId);
            DeleteSheet(db, sheet);
            db.SaveChanges();
        }
    }
    private void DeleteSheet(UranusContext db, Sheet sheet) {
        foreach (var fileDetails in sheet.FileDetails.ToList()) {
            db.FileDetails.Remove(fileDetails);
        }
        foreach (var sheetsCounties in sheet.SheetsCounties.ToList()) {
            db.SheetsCounties.Remove(sheetsCounties);
        }
        db.Sheets.Remove(sheet);
    }
}

最简单的方法是将DbContext作为参数传递:

public class ControllerHelper
{
    public void DeleteChain(int? chainId, UranusContext db)
    {
        var chain = db.Chains.Include(c => c.Sheets)
            .SingleOrDefault(c => c.ChainId == chainId);
        // Removes sheets (children)
        foreach (var sheet in chain.Sheets.ToList())
        {
            DeleteSheet(sheet.SheetId, db);
        }
        db.Chains.Remove(chain);
    }
    public void DeleteSheet(int? sheetId, UranusContext db)
    {
        var sheet = db.Sheets.Include(s => s.FileDetails)
            .Include(s => s.SheetsCounties)
            .SingleOrDefault(s => s.SheetId == sheetId);
        foreach (var fileDetails in sheet.FileDetails.ToList())
        {
            db.FileDetails.Remove(fileDetails);
        }
        foreach (var sheetsCounties in sheet.SheetsCounties.ToList())
        {
            db.SheetsCounties.Remove(sheetsCounties);
        }
        db.Sheets.Remove(sheet);
    }
}

然后像

public void Foo(int? someChainId, int? someSheetId, bool required = false)
{
    ControllerHelper hlp = new ControllerHelper();
    using (UranusContext db = new UranusContext())
    {
        hlp.DeleteChain(someChainId);
        if(_required)
            hlp.DeleteSheet(int? someSheetId);
        db.SaveChanges();
    }
}

尝试使用模式并将上下文作为参数传递给deleetesheet方法，如下:

    public class ControllerHelper
{
    public void DeleteChain(int? chainId)
    {
    using (UranusContext db = new UranusContext())
    {
            var chain = db.Chains.Include(c => c.Sheets)
                .SingleOrDefault(c => c.ChainId == chainId);
            // Removes sheets (children)
            foreach (var sheet in chain.Sheets.ToList())
            {
                DeleteSheet(sheet.SheetId, db);
            }
            db.Chains.Remove(chain);
            db.SaveChanges();
    }
    }
    public void DeleteSheet(int? sheetId, UranusContext db)
    {
        var sheet = db.Sheets.Include(s => s.FileDetails)
            .Include(s => s.SheetsCounties)
            .SingleOrDefault(s => s.SheetId == sheetId);
        foreach (var fileDetails in sheet.FileDetails.ToList())
        {
            db.FileDetails.Remove(fileDetails);
        }
        foreach (var sheetsCounties in sheet.SheetsCounties.ToList())
        {
            db.SheetsCounties.Remove(sheetsCounties);
        }
        db.Sheets.Remove(sheet);
        db.SaveChanges();
    }
}

这样，您就可以确保只有在所有的删除操作完成后才会处理上下文。我总是尽量避免在同一时间使用多个上下文，我以前就被这个问题严重烧伤过!

在您的设计中，ControllerHelper是UranusContext的组合。这意味着您设计了只要ControllerHelper存在，UranusContext就存在，并且您希望UranusCibtext在ControllerHelper不再存在时立即停止存在。

通过使它成为一个组合，你向你的类的用户承诺，只要你的类存在，你的所有函数都可以工作。因此，在用户通知您他们不再需要您的功能之前，您不应该在任何函数中Dispose() UranusContext。这可以通过使您的ControllerHelper IDisposable

如果任何类实现了IDisposable，该类的设计者鼓励用户在不再需要该对象的功能后尽快调用Dispose()。

在你的例子中，代码应该是:

public class ControllerHelper : IDisposable()
{
    private UranusContext db = new UranusContext();
    public void Dispose()
    {
        if (this.db != null)
        {
            this.db.Dispose();
            this.db = null;
        }
        GC.SuppressFinalize(this);
    }
    public void DeleteChain(int? chainId)
    {
       // Do what you need to do, but don't Dispose()
       // nor use using, we want db to be functional
    }
    public void DeleteSheet(int? sheetId)
    {
       // Do what you need to do, but don't Dispose()
       // nor use using, we want db to be functional
    }
}

用法如下:

using (var controllerHelper = new ControllerHelper())
{
    // call functions from controllerhelper
}
// the controllerHelper is not needed anymore, Dispose() is called automatically
// and thus db is Disposed