C# list sort with OR condition-CodePudding

I'm trying to sort a list that comes from my database. If all fields in my OrderFunds column are null, I want to sort by another column. Can anyone tell me how to do this?

This is my code:

List<Fund> funds = await fundSupervisor.List().Where(fund => fund.IsActive)
                                              .OrderBy(fund => fund.OrderFunds)

Or, my OrderBy clause can allow null values. That would help me too.

CodePudding user response：

If you need to sort totally different if, and only if all columns are null, you need to check that in advance.

List<Fund> funds = await fundSupervisor.List().Where(fund => fund.IsActive)
if(funds .Any(item => item.OrderFunds != null))
    funds = funds.OrderBy(fund => fund.OrderFunds);
else
    funds = funds.OrderBy(fund => fund.SomethingElse);

Otherwise, if you want to sort by another value if OrderFunds is null, then you can simply use a condition inside the OrderBy.

var orderedFunds = funds.OrderBy(fund => fund.OrderFunds ?? SomeOtherValue);

If you want to sort by another value as secondary sorting, use a ThenBy. That sorts all values by the ThenBy-value if there are multiple same values in the OrderBy-operation.

var orderedThenByFunds = funds.OrderBy(fund => fund.OrderFunds).ThenBy(fund => fund.SomeOtherValue);

Consider that these lines are different: Say you have 3 items (assumed OrderFunds is int?:

Fund1 { OrderFunds = 1, SomeOtherValue = 8 }
Fund2 { OrderFunds = 3, SomeOtherValue = 6 }
Fund3 { OrderFunds = null, SomeOtherValue = 4 }
Fund4 { OrderFunds = null, SomeOtherValue = 2 }

Then orderedFunds would return Fund1(1), Fund4(2[SomeOtherValue]), Fund2(3), Fund3(4[SomeOtherValue]) and orderedThenByFunds would return Fund1(1,8), Fund2(3,8), Fund4(null,2), Fund3(null,2). The values in braces are the values ordered by.

CodePudding user response：

This is the solution

List<Fund> funds = fundSupervisor
.Where(w => w.IsActive)
.OrderBy(w => w.OrderFunds)
.ThenBy(w => w.OtherField).ToList();

ThenBy() allows you specify other fields to sort your list.