如何检查“id”是空还是空然后默认值是0或空字符串？

Question

我在C＃中使用LINQ编写代码。代码工作正常，但是当我尝试进行测试时，我没有任何价值，因为在没有数据的情况下，我知道如果id为null或空，它将跳过LINQ查询。如果跳过LINQ查询，如何将查询结果的值设置为零或空字符串？

var Rs1 = _context.DwPropertyDetails.Where(x => x.LandId == id && x.TransactionPrice != null) 
        .Select(x => new 
        { 
         Studio = x.FlatType.ToLower() == studio.ToLower() ? x.TransactionPrice : 0, 
         OneBedroom = x.FlatType.ToLower() == onebedroom.ToLower() ? x.TransactionPrice : 0, 
         TwoBedroom = x.FlatType.ToLower() == twobedroom.ToLower() ? x.TransactionPrice : 0, 
         ThreeBedroom = x.FlatType.ToLower() == threebedroom.ToLower() ? x.TransactionPrice : 0, 
         Total = x.TransactionPrice 
        }).Select(a => new 
        { 
         a.Studio, 
         a.OneBedroom, 
         a.TwoBedroom, 
         a.ThreeBedroom, 
         a.Total, 
         Dummy = "x" 
        }).GroupBy(a => new { a.Dummy }) 
        .Select(g => new 
        { 
         Rs1Clm2 = totalTransAmount, 
         Rs1Clm3 = g.Sum(p => p.Studio), 
         Rs1Clm4 = g.Sum(p => p.OneBedroom), 
         Rs1Clm5 = g.Sum(p => p.TwoBedroom), 
         Rs1Clm6 = g.Sum(p => p.ThreeBedroom), 
         Rs1Clm7 = g.Sum(p => p.Total), 
        }); 

好，我尝试在查看

<tbody> 
      @if (Model == null || string.IsNullOrEmpty(Model.Rs1Vms.ToString()) || string.IsNullOrWhiteSpace(Model.Rs1Vms.ToString())) 
      { 
       <tr> 
        <td>Total Transaction Amount</td> 
        <td>0</td> 
        <td>0</td> 
        <td>0</td> 
        <td>0</td> 
        <td>0</td> 
       </tr> 
      } 
      else 
      { 
       foreach (var a in Model.Rs1Vms) 
       { 
        <tr> 
         <td>@Html.DisplayFor(model => a.Rs1Vm2)</td> 
         <td>@($"{a.Rs1Vm3:N0}")</td> 
         <td>@($"{a.Rs1Vm4:N0}")</td> 
         <td>@($"{a.Rs1Vm5:N0}")</td> 
         <td>@($"{a.Rs1Vm6:N0}")</td> 
         <td>@($"{a.Rs1Vm7:N0}")</td> 
        </tr> 
       } 
      } 
     </tbody> 

Answer 1

您可以使用DefaultIfEmpty这项任务。

var Rs2 = Rs1.DefaultIfEmpty(new 
        { 
         Rs1Clm2 = 0, 
         Rs1Clm3 = 0, 
         Rs1Clm4 = 0, 
         Rs1Clm5 = 0, 
         Rs1Clm6 = 0, 
         Rs1Clm7 = 0, 
        });