How to concatenate field in list of objects

Question

I have a list of objects with field String[]. Objects in list >8000 And i need to get String[] with all values from this field from this list

i can do this with loop as below. But can i do this via LINQ (shorter and more efficient) ?

List productInfos = new List();
ProductInfo f1 = new ProductInfo();
f1.tags = new[] { "A","B","T","U"};
ProductInfo f2 = new ProductInfo();
f2.tags = new[] { "C","D","M","U" };
productInfos.Add(f1);
productInfos.Add(f2);

List res = new List();
productInfos.ForEach(f =>
{
    
    foreach (String tag in f.tags)
    {
        res.Add(tag);   
    }
});
res = res.Distinct().ToList();
class ProductInfo
{
    public String[] tags;
}

But can i do this with LINQ ?

Sergey Sosunov · Answer

You can use SelectMany for that.

List res = productInfos.SelectMany(x => x.tags)
    .Distinct()
    .ToList();

Guru Stron · Answer

Just use LINQ all the way (with SelectMany in this particular case):

var res = productInfos
    .SelectMany(p => p.tags)
    .Distinct()
    .ToList();

How to concatenate field in list of objects

2 Answers