How to foreach through a list and get distinct values from specific columns C#?

Question

I'm able to loop through a list on sharepoint and get the information I need from selected columns, but how would I loop through a list and get only distinct values from a column in C#. For instance lets get all the distinct values from a the email column?

I know I can foreach through the list

foreach (SPListItem item in List.getItems(querysp)
{
var itemID = item.ID;
var itemEmail = item["email"];
...

//more vars here

...

}

Answer 1

You can get Distinct values for email column from your SharePoint list using below mentioned code. i had showed how to insert the distinct email values in drop down list. you can change the code accordingly.

try
{
 SPList oList = SPContext.Current.Web.Lists["Your List Nmae Here"];
 SPQuery query = new SPQuery();
 query.Query = "<OrderBy><FieldRef Name='Email' /></OrderBy>";
 DataTable dtcamltest = oList.GetItems(query).GetDataTable();
 DataView dtview = new DataView(dtcamltest);
 DataTable dtdistinct = dtview.ToTable(true, "Email");
 ddl_names.DataSource = dtdistinct; 
 ddl_names.DataTextField = "Email";
 ddl_names.DataValueField = "Email";
 ddl_names.DataBind();                           
}
catch (Exception exe)
{
 Response.Write("Exception at btn_binddropdown_Click :" + exe);
}

Answer 2

I don't know if it is possible with CAML, but this should work:

var emails = List.getItems(querysp).OfType<SPListItem>().Select(item => "" + item["email"]).Distinct();