How to get Rid of Duplicate Keys in Dictionary C#

I keep on getting the error: Item has already been added. Key in dictionary: '@QueryID' Key being added: '@QueryID'. I did some research on this and it tells me that I'm inserting duplicate keys into a dictionary object. Dictionary objects in .Net can only have unique keys. I don't know how to get rid of duplicate keys.

class Program
{
   private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    static void Main()
    {
        EMMADatabase db = new EMMADatabase(""); //set string to pass in based on App.config


        try
        {
            Hashtable Parameters = new Hashtable();
            //Parameters.Add("@UserCredentials", UserCredentials);

            DataTable result = db.Query("exec Metrics_ETL.dbo.uspDetermineQueriesToRunBasedOnSchedules", Parameters);
            DataTable QueriesToRun = db.Query("select QueryID from Metrics_ETL.dbo.QueriesToRun", Parameters);

            foreach(DataRow row in QueriesToRun.Rows)
            {
                Hashtable QueryParameters = new Hashtable();
                Parameters.Add("@QueryID", row["QueryID"]);
                DataTable QueryDetails = db.Query("select QueryID, Query, ObjectID, DataSourceID, DatabaseName, ServerName, ServerType, UserName, Password from Metrics_ETL.dbo.Queries where QueryID = @QueryID", Parameters);

                //log.Info(row["QueryID"]);
                //Console.WriteLine(row["QueryID"]);

                //create datasource - query datasource - get data into a datatable

                //write datatable to csv with correct filename (OR maybe C# can write to Excel)
            }



        }
        catch(Exception e)
        {
            Console.WriteLine("Error: " + e);
        }
        finally
        {
            Console.Read();
        }
    }

I think this is where the @QueryID value is added, but wasn't sure. I am a beginner to programming so I am very noob at this. Any suggestion would greatly be appreciated.

 private DataTable QueryToDataTable(string QueryString, Hashtable Parameters)
    {
        DataTable dt = new DataTable();

        using (new Impersonator("svc-emma-admin", "1dc", "618MId}QM"))
        {
            SqlCommand cmd = new SqlCommand(QueryString, DBConnection);
            cmd.CommandTimeout = 120;

            foreach (DictionaryEntry Parameter in Parameters)
            {
                cmd.Parameters.Add((string)Parameter.Key, SqlDbType.NVarChar);
                cmd.Parameters[(string)Parameter.Key].Value = Parameter.Value;
            }

            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(dt);
        }

        return dt;
    }