Search code examples
c#listoptimizationsonarqube

Code Optimisation - remove this expression which always evaluates to "true"

I am trying to optimize the code using SonarQube

List<string> itemList = serviceObject.GetItems();

I tried to validate the list with the below code

if(itemList != null && itemList.Any()
{
     //Some operations
}

when above code executed I am getting Sonarqube error remove this expression which always evaluates to "true" So I refactor the code as

if(itemList == null || !itemList.Any())
    return;
//Some Operations

when above code executed I am getting Sonarqube error remove this expression which always evaluates to "false"

Could anyone let me know what is wrong here?

Solution

  • You can shorten this to

    if (itemList?.Count >0)
{
...
}

    or

    if (itemList?.Any() ==true)
{
...
}

    ?. is one of the Null conditional operators (the other is ?[]), the Elvis operator for short, that allows you to access potentially null variables without throwing. The result of the entire expression after the Elvis operator is nullable and returns null if the variable is null.

    This means that itemList?.Count returns an Nullable<int>, and itemList?.Any() a Nullable<bool>. Nullable<T> defines relational operators between itself and its base type T but can't be used as T without an explicit cast. That's why (itemList?.Any() ==true) is needed.

    If you use Nullable Reference Types though, itemList can't be null, so a simple comparison would be enough:

    if (itemList.Count >0)
{
...
}

    If you enable Nullable Reference Types by setting #nullable enable in a source file or <Nullable>enable</Nullable> in the csproj file, the compiler ensures that all variables, fields and methods that return reference types are not null, forcing you to either fix the problem or explicitly specify that a variable is nullable.

    With NRTs enabled this line :

    List<string> itemList = serviceObject.GetItems();

    Would only compile without warnings if GetItems never returned a null. If the compiler doubts this, it would issue a warning advising you to either fix the problem or explicitly declare itemList as nullable with :

    List<string>? itemList = serviceObject.GetItems();