Finding Data Using Linq for a Dataset

Question

I have user information. I am trying to perform a search that can use a name, user id, or user role. I have a search text box for the name and identifier and a drop-down list for the search for the user role. Not everyone can be empty, but any combination can be used. I use the following, but I don’t think it’s correct, since it always returns the whole data type:

dtUsers.CaseSensitive = false;
var results = dtUsers.AsEnumerable()
    .Where(r => r.Field<String>("LASTNAME").Contains(tbName.Text.Trim())
           ||   r.Field<String>("USERID").Contains(tbUserID.Text.Trim())
           ||   r.Field<String>("USERROLELIST").Contains(ddlRoles.SelectedItem.Text));            

dtUsers = results.CopyToDataTable();

What am I doing wrong? I also need to be able to do a partial search by name and id.

Answer 1

, ( String.IsNullOrWhiteSpace) :

var results = dtUsers.AsEnumerable()
    .Where(r =>(!String.IsNullOrWhiteSpace(tbName.Text) && r.Field<String>("LASTNAME").Contains(tbName.Text.Trim())
           || (!String.IsNullOrWhiteSpace(tbUserID.Text) &&r.Field<String>("USERID").Contains(tbUserID.Text.Trim())
           || r.Field<String>("USERROLELIST").Contains(ddlRoles.SelectedItem.Text));

, :

(ddlRoles.SelectedItem != null && 
 !String.IsNullOrWhiteSpace(ddlRoles.SelectedItem.Text) && 
  r.Field<String>("USERROLELIST").Contains(ddlRoles.SelectedItem.Text)