Getting error while adding datasource name at the time of installing windows application

public override void Install(System.Collections.IDictionary stateSaver)
        {
            try
            {
                string dataSource = "Data Source =" + Context.Parameters["DataSource"];
                string initialcatalog = "Initial Catalog=" + Context.Parameters["InitialCatalog"];
                dataSource = dataSource + ";" + initialcatalog;
                dataSource = dataSource + ";Integrated Security=SSPI;";
                MessageBox.Show("instance=" + dataSource);
                ExeConfigurationFileMap map = new ExeConfigurationFileMap();
                MessageBox.Show(Assembly.GetExecutingAssembly().Location + ".config");
                //Getting the path location 
                string configFile = string.Concat(Assembly.GetExecutingAssembly().Location, ".config");
                map.ExeConfigFilename = configFile;
                System.Configuration.Configuration config = System.Configuration.ConfigurationManager.
                OpenMappedExeConfiguration(map, System.Configuration.ConfigurationUserLevel.None);
                string connectionsection = config.ConnectionStrings.ConnectionStrings
                ["SqlConnectionString"].ConnectionString;

                ConnectionStringSettings connectionstring = null;
                if (connectionsection != null)
                {
                    config.ConnectionStrings.ConnectionStrings.Remove("SqlConnectionString");
                    MessageBox.Show("removing existing Connection String");
                }

                connectionstring = new ConnectionStringSettings("SqlConnectionString", dataSource);
                config.ConnectionStrings.ConnectionStrings.Add(connectionstring);

                config.Save(ConfigurationSaveMode.Modified, true);
                ConfigurationManager.RefreshSection("connectionStrings");
            }
            catch (Exception ex)
            {
                throw new InstallException("A forced exception", ex);
            }
        }