how can read Specified column or All the columns of checked SelectionModel in Grid

[TAYMA]

hi
I'm going to get the value of all the checked rows in the Grid. I followed this example https://mvc.ext.net/#/GridPanel_Spreadsheet/Submit/

 .SelectionModel(
              Html.X()
                  .CheckboxSelectionModel().ID("Model1")
                  .Mode(SelectionMode.Multi)

          )

and

.DirectEvents(de =>
                      {
                          de.Click.Action = "Submit";
                          de.Click.EventMask.ShowMask = true;
                          de.Click.ExtraParams.Add(new Parameter()
                          {
                              Name = "selection",
                              Value= "App.Model1.getSubmitData({ excludeId: true })" ,
                              Mode = ParameterMode.Raw  
                          });
                      }) )

but js error occurs With this theme : "Uncaught TypeError: App.Model1.getSubmitData is not a function"
i think getSubmitData only work for SpreadsheetSelectionModel but i have a CheckboxSelectionModel
is it possible someone give me a sample for getting value of checked row of grid in viewpage for using in codebehiend