var result = sourcelist
             .Select(x => new Model() 
                 { 
                    col1 = (x.col2 == "True" && x.col3 == "True" == x.col4 == "True") ? "1" : "2",
                    col2 = x.col2,
                    col3 = x.col3,
                    col4 = x.col4
                 });

------解决方案--------------------

C# code

void Main()
{
    var result = new List<Model>{
        new Model { col1 = "1",col2 = "True",col3 = "True",col4 = "True"},
        new Model { col1 = "2",col2 = "True",col3 = "False",col4 = "True"},
        new Model { col1 = "2",col2 = "True",col3 = "False",col4 = "False"}
        };
    var query=result.GroupBy(r=>new {r.col2,r.col3,r.col4})
                    .Select(g=>new Model{ 
                        col1=g.FirstOrDefault().col1,
                        col2=g.Key.col2=="True"?"1":"2",
                        col3=g.Key.col3=="True"?"1":"2",
                        col4=g.Key.col4=="True"?"1":"2"
                    });
        Console.WriteLine(query);
}

class Model
{
public string col1 {get;set;}
public string col2 {get;set;}
public string col3 {get;set;}
public string col4 {get;set;}
}