.net - DataGridViewComboBox and Gridview -

i have gridview , have 1 column datagridviewtextboxcolumn. when assign datasource grid error:

datagridview default error dialog

the following exception occurred in datagridview:

system.formatexception: datagridviewcomboboxcell value not valid. 

to replace default dialog please handle dataerror event.

ok

i don't see why is..

this first class:

    public class floraitem     {        public guid id { get; set; }        public string name { get; set; }        public int price { get; set; }        public datetime expirationdate { get; set; }        public category categoryitem { get; set; }     } 

this class datasource of grid

the category class looks like:

   public class category    {      public guid id { get; set; }      public string name { get; set; }      public bool addbreakstoprint { get; set; }    } 

the datasource of dropdown (combobox) in grid have category datasource..

this initializecomponent function

    private void initializecomponent()     {         this.components = new system.componentmodel.container();         this.grdfloraitems = new system.windows.forms.datagridview();         this.floraitembindingsource = new system.windows.forms.bindingsource(this.components);         this.categorybindingsource2 = new system.windows.forms.bindingsource(this.components);         this.lstcategories = new system.windows.forms.combobox();         this.label1 = new system.windows.forms.label();         this.namedatagridviewtextboxcolumn = new system.windows.forms.datagridviewtextboxcolumn();         this.pricedatagridviewtextboxcolumn = new system.windows.forms.datagridviewtextboxcolumn();         this.expirationdatedatagridviewtextboxcolumn = new system.windows.forms.datagridviewtextboxcolumn();         this.categoryitem = new system.windows.forms.datagridviewcomboboxcolumn();         ((system.componentmodel.isupportinitialize)(this.grdfloraitems)).begininit();         ((system.componentmodel.isupportinitialize)(this.floraitembindingsource)).begininit();         ((system.componentmodel.isupportinitialize)(this.categorybindingsource2)).begininit();         this.suspendlayout();         //          // grdfloraitems         //          this.grdfloraitems.allowusertodeleterows = false;         this.grdfloraitems.autogeneratecolumns = false;         this.grdfloraitems.columnheadersheightsizemode = system.windows.forms.datagridviewcolumnheadersheightsizemode.autosize;         this.grdfloraitems.columns.addrange(new system.windows.forms.datagridviewcolumn[] {         this.namedatagridviewtextboxcolumn,         this.pricedatagridviewtextboxcolumn,         this.expirationdatedatagridviewtextboxcolumn,         this.categoryitem});         this.grdfloraitems.datasource = this.floraitembindingsource;         this.grdfloraitems.location = new system.drawing.point(12, 55);         this.grdfloraitems.name = "grdfloraitems";         this.grdfloraitems.readonly = true;         this.grdfloraitems.size = new system.drawing.size(652, 206);         this.grdfloraitems.tabindex = 1;         //          // floraitembindingsource         //          this.floraitembindingsource.datasource = typeof(data.floraitem);         //          // categorybindingsource2         //          this.categorybindingsource2.datasource = typeof(data.category);         //          // namedatagridviewtextboxcolumn         //          this.namedatagridviewtextboxcolumn.datapropertyname = "name";         this.namedatagridviewtextboxcolumn.headertext = "artikel";         this.namedatagridviewtextboxcolumn.name = "namedatagridviewtextboxcolumn";         this.namedatagridviewtextboxcolumn.readonly = true;         this.namedatagridviewtextboxcolumn.width = 250;         //          // pricedatagridviewtextboxcolumn         //          this.pricedatagridviewtextboxcolumn.datapropertyname = "price";         this.pricedatagridviewtextboxcolumn.headertext = "prijs";         this.pricedatagridviewtextboxcolumn.name = "pricedatagridviewtextboxcolumn";         this.pricedatagridviewtextboxcolumn.readonly = true;         //          // expirationdatedatagridviewtextboxcolumn         //          this.expirationdatedatagridviewtextboxcolumn.datapropertyname = "expirationdate";         this.expirationdatedatagridviewtextboxcolumn.headertext = "verloop datum";         this.expirationdatedatagridviewtextboxcolumn.name = "expirationdatedatagridviewtextboxcolumn";         this.expirationdatedatagridviewtextboxcolumn.readonly = true;         this.expirationdatedatagridviewtextboxcolumn.width = 150;         //          // categoryitem         //          this.categoryitem.datapropertyname = "categoryitem";         this.categoryitem.datasource = this.categorybindingsource2;         this.categoryitem.displaymember = "name";         this.categoryitem.headertext = "categorie";         this.categoryitem.name = "categoryitem";         this.categoryitem.readonly = true;         this.categoryitem.resizable = system.windows.forms.datagridviewtristate.true;         this.categoryitem.sortmode = system.windows.forms.datagridviewcolumnsortmode.automatic;         this.categoryitem.valuemember = "id";         //          // editfloraitem         //          this.autoscaledimensions = new system.drawing.sizef(6f, 13f);         this.autoscalemode = system.windows.forms.autoscalemode.font;         this.clientsize = new system.drawing.size(696, 273);         this.controls.add(this.label1);         this.controls.add(this.lstcategories);         this.controls.add(this.grdfloraitems);         this.name = "editfloraitem";         this.text = "editfloraitem";         this.controls.setchildindex(this.grdfloraitems, 0);         this.controls.setchildindex(this.lstcategories, 0);         this.controls.setchildindex(this.label1, 0);         ((system.componentmodel.isupportinitialize)(this.grdfloraitems)).endinit();         ((system.componentmodel.isupportinitialize)(this.floraitembindingsource)).endinit();         ((system.componentmodel.isupportinitialize)(this.categorybindingsource2)).endinit();         ((system.componentmodel.isupportinitialize)(this.categorybindingsource1)).endinit();         ((system.componentmodel.isupportinitialize)(this.categorybindingsource)).endinit();         this.resumelayout(false);         this.performlayout();        } 

this i'm stuck..

category needs collection (like list) not single item.
, call categories.