Getting Sql Query In C# Code

Dear All


I am a beginner and looking for some help. I have a database with just one column (some names). That is the primary key aswell. Because I want the names to be unique.
I used a grid view control to display the data and included the insert functionality in the grid view by using some code and the part of the code that does the insert is
  1 public static void Insert(Categories category)
2 {
3 string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
4 using (IDbConnection cn = new SqlConnection(connectionString))
5 {
6 cn.Open();
7
8 IDbCommand cmd = new SqlCommand();
9
10 cmd.CommandText = "INSERT INTO Categories (CategoryName) VALUES " +
11 "('" + category.CategoryName + "')";
12
13 cmd.Connection = cn;
14 cmd.ExecuteNonQuery();
15 }
16 }

 
Question: when someone tried to enter a new name which already exists in the database it throws an error page which is what I want but is there a way to be able to display the user a message sayin g that he/she has entered a name that already exists and hence they need to try a different name? instead of the ugly error page?
 
Thank you in advance,
Prasad.