member names cannot be the same as their enclosing type

in sub class i can't define a constructor it give me error when i want it
to...
"category member names cannot be the same as their enclosing type"

namespace Database
{
public class Structure
{
public class category
{
public int category_id;
public int category_belong_id;
public string category_name;
public string DisplayMember{ get{ return category_name; } }
public string ValueMember{ get{ return category_id.ToString(); } }

public void category(){}
public void category(Database.Query sender)
{
this.category_id = sender.myReader.GetInt32(0);
this.category_belong_id = sender.myReader.GetInt32(1);
this.category_name = sender.myReader.GetString(2);
sender.myReader.Close();
sender.myConnection.Close();
}
}
}

i got it.. even no void for constructors