asp.net - Linq，如何检查字段的值是否为空

Question

在使用 linq 查询时我收到错误

System.NullReferenceException: Object reference not set to an instance of an object.

var db = from d in DepartmentBLL.GetDepartmentList()
     join b in BudgetMasterBLL.GetBudgetMasterList()            
     on d.Departmentid equals b.Departmentid into leftJoin                     
     from results in leftJoin.DefaultIfEmpty()
     select new
     {
         Name = d.Name,
         Create = results.Budgetmasterid == null ? "null": "value", //ERROR HERE
         CreateURL = "frmBudgetInitial.aspx?departmentid=" + d.Departmentid.ToString() + "&departmentcategoryid=" + d.Departmentcategoryid.ToString()
     };

我在论坛上找到了一些帮助，但没有解决我的问题，请指教。谢谢，

Answer 1

尝试

Create = results == null || string.IsNullOrEmpty(results.Budgetmasterid) ? "null": "value",

或

Create = results == null || string.IsNullOrWhitespace(results.Budgetmasterid) ? "null": "value",