The name 'VarPerc' does not exist in the current context

[orcim]

Un saluto a tutti e grazie del vostro tempo.

Dovrei valorizzare l'output di questa query select in mysql, ma mi dà errore, cosa sbaglio?

Compiler Error Message: CS0103: The name 'VarPerc' does not exist in the current context
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1

       String myQuery = " SELECT " +
                         " CONCAT(VariazionePercentuale,'%') As VarPerc " +                         
                         " FROM tbl_m " +
                         " WHERE " +
                         " tNome LIKE '%Pippo%'; ";


       OdbcConnection myConnectionString = 
       new OdbcConnection(
       ConfigurationManager.ConnectionStrings["ConnMySQL"].ConnectionString);
       myConnectionString.Open();
       
       OdbcCommand objCmd = new OdbcCommand(myQuery, myConnectionString);
       objCmd.Prepare();
       objCmd.CommandType = CommandType.Text;
       objCmd.CommandText = myQuery;

       objCmd.Parameters.Add("?VarPerc", OdbcType.Text).Value = VarPerc.ToString();
       
       Chart1.DataSource = objCmd.ExecuteReader();