C# linq query aggregate nullable boolean

Question

I'd like to use linq to aggregate a nullable bool following the logic:

• If all is true then true;
• if all is false then false;
• else null

Here is my code, I couldn't get the bool aggregate.

class T1
{
  public string property1{get;set;}
  public string property2{get;set;}
  public bool? BoolProperty{get;set;}
}

///initialize a list<T1> t2 with values......
List<T1> t2 = new List<T1>();
t2.Add(new T1() 
        {
            property1="hello",
            property2="world",
            BoolProperty=true
        });
t2.Add(new T1() 
        {
            property1="hello",
            property2="world",
            BoolProperty=false
        });

List<T1> t1 = t2.GroupBy(g => new
        {
            g.property1,
            g.property2               
        })
        .Select(g => new T1
        {
            property1 = g.Key.property1,
            property2 = g.Key.property2,                
            BoolProperty = ////can someone help? if all object in t2 are true, true; if all object in t2 are false, false; else null
 ///in this case i am expecting a null
        }).ToList();

So t1 will be "hello", "world", null; Thanks

Answer 1

How about this?

BoolProperty = g.All(p => p.BoolProperty.GetValueOrDefault())
    ? true
    : (g.All(p => !(p.BoolProperty ?? true))
        ? (bool?)false
        : null)
            }).ToList();

Answer 2

Put this in your code,

List<T1> t1 = t2.GroupBy(g => new
        {
            g.property1,
            g.property2               
        })
        .Select(g => new T1
        {
            property1 = g.Key.property1,
            property2 = g.Key.property2,                
            BoolProperty =  g.GroupBy(grp => grp.BoolProperty).Count() > 1 ? null : g.Select(g_val=>g_val.BoolProperty).First()
        }).ToList();