Cannot format nullable decimal using ToString("#.##") - linq

Question

How do I format a nullable decimal such that it's string output is formatted to two decimal places?
Salary = g.Where(x => !String.IsNullOrEmpty(x.Salary))
.Select(x => (decimal?)decimal.Parse(x.Salary))
.DefaultIfEmpty(null)
.Sum().ToString();
The above works but sometimes yields a decimal results that is very long
203827.82763651324038269
I would like to format the result to two decimal places
203827.83
Since my desired output is a string I thought I could just use
.Sum().ToString("#.##);
Bu t I get an error No overload for method 'ToString' takes 1 arguments which I think is due to the results being a nullable decimal. How do I work around this?

Answer 1

You are right, Nullable(T).ToString() doesn't take any arguments. Instead, you can use good old fashioned string.Format or the string interpolation shorthand:
var result = g.Where(x => !String.IsNullOrEmpty(x.Salary))
.Select(x => (decimal?)decimal.Parse(x.Salary))
.DefaultIfEmpty(null)
.Sum();
Salary = $"{result:#.###}";
However, it's not clear why you are casting to decimal? here, why not simply this:
Salary = g.Where(x => !String.IsNullOrEmpty(x.Salary))
.Select(x => decimal.Parse(x.Salary))
.Sum()
ToString("#.###");
Of course, I would suggest keeping the x.Salary values as decimal rather than string, but that's a different story.

Answer 2

Yes, you're right. The nullable decimal's ToString doesn't take any parameters and has no overloads. You need to access the Value of the nullable decimal:
var Salary = g.Where(x => !String.IsNullOrEmpty(x.Salary))
.Select(x => (decimal?)decimal.Parse(x.Salary))
.DefaultIfEmpty(null)
.Sum();
var result=Salary.HasValue?Salary.Value.ToString("#:##"):"";