Where clause in C# linq to datatable

Question

I have two columns with Col1 and col2 in data table like below:

note:

col1 contains only us or uk, no other values

Now my requirement is to separate the values based on us and uk.

Like below get all the values corresponding to us and uk seperately.

Earlier I have done this with linq code. At that time my requirement is a simple one,

just get all the records in col2:

string[] data = dt.AsEnumerable()
  .Select(s => s.Field<string>("col2"))
  .ToArray<string>();

now in the new requirement I need them separately based on us and uk.

Answer 1

When you need to separate your items based on a value of some column, you use GroupBy, like this:

var groups = dt.AsEnumerable().GroupBy(s => s.Field<string>("col1"));

Once you have your groups, you can iterate them, or "materialize" them in a Dictionary<string,string[]>, like this:

var byCol1 = groups.ToDictionary(g => g.Key, g => g.Select(s => s.Field<string>("col2")).ToArray());

You can output the numbers for each key like this:

foreach (var p in byCol1) {
    Console.WriteLine("{0} : {1}", p.Key, string.Join(", ", p.Value));
}

or get the numbers for a specific key like this:

string[] items = byCol1["us"];

Answer 2

To get a list of all col2 values where col1 is equal to "us", you could use code like this:

string[] data = dt.AsEnumerable().Where(s => s.Field("col1") == "us").Select(s => s.Field("col2")).ToArray();