Insert Selected item in listbox using Ado.net and stor proc
If you are using the Enterprise Library it is often better to set up a default connection in the configuration file:

&lt;configuration&gt;
  &lt;configSections&gt;
    &lt;section name="dataConfiguration" 
       type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings,
            Microsoft.Practices.EnterpriseLibrary.Data, Version=5.0.414.0, 
            Culture=neutral, PublicKeyToken=null" 
        requirePermission="false"/&gt;
  &lt;/configSections&gt;

  &lt;dataConfiguration defaultDatabase="SiteSqlServer" /&gt;

  &lt;!-- Rest of your settings here, including your SiteSqlServer connection string --&gt;
&lt;/configuration&gt;


Now you don't need to look up the connection string - you can rely on the Enterprise library to get it for you:

public static void Insert(IEnumerble&lt;int&gt; skills, int resourceId)
{
    // No dependency on SQL anymore - the connection string is found
    // from the dataConfiguration section in your config file. If you change
    // to another (supported) provider, you don't need to change this code.
    Database db = DatabaseFactory.CreateDatabase();

    // Add in your schema to the stored proc name (I've assumed dbo).
    using (var cmd = db.GetStoredProcCommand("dbo.Insert_Skills_Resources"))
    {
        // This method populates the parameters collection of the DbCommand
        // by interrogating the database about the command.
        db.DiscoverParameters(cmd);

        // As the parameters are now known, we can just set the value of 
        // them directly, no need specify direction or type etc.
        cmd.Parameters["ResourceID"].Value = resourceId;

        foreach (var skill in skills)
        {
            cmd.Parameters["SkillID"].Value = skill;
            db.ExecuteNonQuery(cmd);
                    // Don't need to clear the parameters now.
        }
        // &lt;Pointless try catch removed.&gt;
    }
}   


EDIT:

Sorry, it's been a year or more since I used the Enterprise Library I can't remember whether you need the @ at the start of the parameter name or not - it might be cmd.Parameters["@SkillID"].

EDIT 2:

I remembered why I couldn't remember if you need the @ or not (if that makes sense). You do need the @ BUT, you should use the Database.BuildParameterName method to create the parameter in the format the current provider expects - for sql server this is an @ symbol before the parameter name.

This is how you should do it:

cmd.Parameters[db.BuildParameterName("ResourceID")].Value = resourceId;


With this final correction the code is actually ignorant of the provider!