WPF trigger on datagrid to hide/show columns according to bindings -

i have data grid this:

<datagrid autogeneratecolumns="false" canuserdeleterows="true"           horizontalscrollbarvisibility="hidden" margin="10,10,10,10"            verticalscrollbarvisibility="visible"            canuseraddrows="false" itemssource="{binding listgestores}"           tooltip="selecione uma linha e pressione delete para remover uma unidade.">     <datagrid.columns>         <datagridtextcolumn binding="{binding tb_unidade.ds_nome_unidade}" canuserresize="false" header="setor" isreadonly="true" x:name=""/>         <datagridtextcolumn binding="{binding tb_unidade.tb_unidade2.ds_nome_unidade}" canuserresize="false" header="unidade" isreadonly="true" x:name=""/>         <datagridtextcolumn binding="{binding tb_contatos.ds_nome}" canuserresize="false" header="gestor" isreadonly="true" />     </datagrid.columns> </datagrid> 

the problem need verify if 2 column binding null, , if null, need hide it, , change header of column 1.

i know can triggers, how exactly??? started with:

<datagrid.triggers>     <datatrigger binding="{binding tb_unidade.tb_unidade2}" value="{x:null}">         <setter property="" value="" />     </datatrigger> </datagrid.triggers> 

but don't know setter or whatever put !

help me =]

example:

with following viewmodel:

public class viewmodel : inotifypropertychanged {     public string data1 { get; set; }     public string data2 { get; set; }     public string data3 { get; set; } } 

you can use following sample xaml:

<grid.resources>     <local:datagridcolumnvisibilityconverter x:key="datagridcolumnvisibilityconverter" /> </grid.resources> <datagrid>     <datagrid.columns>         <datagridtextcolumn binding="{binding data1}"                             visibility="{binding, converter={staticresource datagridcolumnvisibilityconverter}, converterparameter=data1}" />         <datagridtextcolumn binding="{binding data2}"                             visibility="{binding, converter={staticresource datagridcolumnvisibilityconverter}, converterparameter=data2}" />         <datagridtextcolumn binding="{binding data3}"                             visibility="{binding, converter={staticresource datagridcolumnvisibilityconverter}, converterparameter=data3}" />     </datagrid.columns> </datagrid> 

and converter:

public class datagridcolumnvisibilityconverter : ivalueconverter {     public object convert(object value, type targettype, object parameter, system.globalization.cultureinfo culture)     {         viewmodel viewmodel = (viewmodel)value;          switch (parameter.tostring().tolower())         {             case "data1":                 return (!string.isnullorempty(viewmodel.data1)) ? visibility.visible : visibility.collapsed;             case "data2":                 return (!string.isnullorempty(viewmodel.data2)) ? visibility.visible : visibility.collapsed;             case "data3":                 return (!string.isnullorempty(viewmodel.data3)) ? visibility.visible : visibility.collapsed;         }          return visibility.visible;     }      public object convertback(object value, type targettype, object parameter, system.globalization.cultureinfo culture)     {         throw new notimplementedexception();     } }