如何避免长if-else链中的重复代码？

Question

我正在使用带有实体框架工作的web api 2。在一个条件下，我想知道如何减少if/else相同的代码。我努力了，但我没有得到任何结果。我正在使用lambada表达。

   //  ALL Value Is Given By User

        if (FightTypeId != 0 && Title != null && Date != null)
        {
            var getTblEvent = db.tblEvents.Where(e => e.FightTypeId == FightTypeId && e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()) && e.Date == Date);

            //this illustrates that user can  give title in any case  and title can be in  2-3 latter of title is enough for  get output

            var res = from e in getTblEvent
                      select new
                      {
                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,


                      };
            return Ok(res);


        }

         //Only FightTypeID Is Given By User

        else if (FightTypeId != 0 && Title == null && Date == null)
        {

            var getTblEvent = db.tblEvents.Where(e => e.FightTypeId == FightTypeId);
            var res = from e in getTblEvent
                      select new
                      {


                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,


                      };
            return Ok(res);
        }

          //TITLE Is Given By User


        else if (FightTypeId == 0 && Title != null && Date == null)
        {

            var getTblEvent = db.tblEvents.Where(e => e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()));
            var res = from e in getTblEvent
                      select new
                      {

                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,

                      };
            return Ok(res);
        }

       // Only DATE Is Given By User

        else if (FightTypeId == 0 && Title == null && Date != null)
        {

            var getTblEvent = db.tblEvents.Where(e => e.Date == Date);
            var res = from e in getTblEvent
                      select new
                      {

                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,


                      };
            return Ok(res);
        }

        //FIGHTTYPEID And TITLE Is Given By User


        else if (FightTypeId != 0 && Title != null && Date == null)
        {

            var getTblEvent = db.tblEvents.Where(e => e.FightTypeId == FightTypeId && e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()));
            var res = from e in getTblEvent
                      select new
                      {


                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,

                      };
            return Ok(res);
        }


         // Only DATE And TITLE Is Given By User

        else if (FightTypeId == 0 && Title != null && Date != null)
        {

            var getTblEvent = db.tblEvents.Where(e=>e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()) && e.Date==Date);
            var res = from e in getTblEvent
                      select new
                      {

                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,

                      };
            return Ok(res);
        }



        //FightTypeID And Date Is Given By User

        else if (FightTypeId != 0 && Title == null && Date != null)
        {

            var getTblEvent = db.tblEvents.Where(e => e.FightTypeId==FightTypeId && e.Date==Date);
            var res = from e in getTblEvent
                      select new
                      {


                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,


                      };
            return Ok(res);
        }

            // by defaultly  shows all Details to user
        else
        {

            var res = from e in db.tblEvents
                      select new
                      {

                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,


                      };
            return Ok(res);
        }

    }

Answer 1

看起来你只是在检查每个参数是否存在，如果它们不是null（或0），你可以通过它进行过滤。您可以检查每个参数并链接Where次来完成您想要的操作：

var query = db.tblEvents;

if(FightTypeId != 0)
{
    query = query.Where(e => e.FightTypeId == FightTypeId);
}

if(Title != null)
{
    query = query.Where(e => e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()));
}

if(Date != null)
{
    query = query.Where(e => e.Date == Date);
}

var res = query.Select(e =>
                      new
                      {
                          EventID = e.EventID,
                          FightTypeId = e.FightTypeId,
                          Title = e.Title,
                          Date = e.Date,
                          Location = e.Location,
                          UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                          Price = e.Price,
                          UserPredictionFlag = e.UserPredictionFlag,
                          PredictionStartDate = e.PredictionStartDate,
                          PredictionEndDate = e.PredictionEndDate,
                          ModifiedUserId = e.ModifiedUserId,
                          LastUserModifiedDate = e.LastUserModified,
                      };

return Ok(res);

Answer 2

你可以这样简化它：

   // by defaultly  shows all Details to user
   var getTblEvent = db.tblEvents;
   //  ALL Value Is Given By User

        if (FightTypeId != 0 && Title != null && Date != null)
        {
            getTblEvent = db.tblEvents.Where(e => e.FightTypeId == FightTypeId && e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()) && e.Date == Date);
        }


         //Only FightTypeID Is Given By User

        else if (FightTypeId != 0 && Title == null && Date == null)
        {

            getTblEvent = db.tblEvents.Where(e => e.FightTypeId == FightTypeId);
        }

          //TITLE Is Given By User


        else if (FightTypeId == 0 && Title != null && Date == null)
        {

           getTblEvent = db.tblEvents.Where(e => e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()));

        }

       // Only DATE Is Given By User

        else if (FightTypeId == 0 && Title == null && Date != null)
        {

           getTblEvent = db.tblEvents.Where(e => e.Date == Date);
        }

        //FIGHTTYPEID And TITLE Is Given By User


        else if (FightTypeId != 0 && Title != null && Date == null)
        {

           getTblEvent = db.tblEvents.Where(e => e.FightTypeId == FightTypeId && e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()));

        }


         // Only DATE And TITLE Is Given By User

        else if (FightTypeId == 0 && Title != null && Date != null)
        {

           getTblEvent = db.tblEvents.Where(e=>e.Title.ToUpper().Trim().Contains(Title.ToUpper().Trim()) && e.Date==Date);

        }



        //FightTypeID And Date Is Given By User

        else if (FightTypeId != 0 && Title == null && Date != null)
        {

           getTblEvent = db.tblEvents.Where(e => e.FightTypeId==FightTypeId && e.Date==Date);

        }


        var res = from e in getTblEvent
                  select new
                  {

                      EventID = e.EventID,
                      FightTypeId = e.FightTypeId,
                      Title = e.Title,
                      Date = e.Date,
                      Location = e.Location,
                      UserSelectFavoriteFlag = e.UserSelectFavoriteFlag,
                      Price = e.Price,
                      UserPredictionFlag = e.UserPredictionFlag,
                      PredictionStartDate = e.PredictionStartDate,
                      PredictionEndDate = e.PredictionEndDate,
                      ModifiedUserId = e.ModifiedUserId,
                      LastUserModifiedDate = e.LastUserModified,


                  };
        return Ok(res);