dxg:GridControl Name="gridControl_grafik" FlowDirection="LeftToRight">
            <dxg:GridControl.View>
                <dxg:TableView AllowColumnFiltering="True" AllowHorizontalScrollingVirtualization="False" AutoScrollOnSorting="False" BestFitMode="VisibleRows" />
            </dxg:GridControl.View>
        </dxg:GridControl>

for (int i = 1; i <= ResourceWrapper.CurrentDomainContext.rb_months.Count; i++)
            {
                var record_groups = ResourceWrapper.CurrentDomainContext.rb_months.FirstOrDefault(r => r.indx == i);
                if (record_groups != null)
                {
                    GridColumn columns_grafik = new GridColumn()
                    {
                        FieldName = record_groups.name
                    };
                    gridControl_grafik.Columns.Add(columns_grafik);
                }
            }

январь    февраль ... декабрь

Имя   январь     февраль   ...  декабрь
1     1 2 3 4    5 6 7 8   ...  . . . . 
2     1 2 3 4    5 6 7 8   ...  . . . . 
3     1 2 3 4    5 6 7 8   ...  . . . . 

<dxg:GridControl x:Name="grid" ItemsSource="{Binding}" Margin="5">
        <dxg:GridControl.View>
            <dxg:TableView>
                <i:Interaction.Behaviors>
                    <dxgext:BandedViewBehavior>
                        <dxgext:BandedViewBehavior.ColumnDefinitions>
                            <dxgext:ColumnDefinition Width="*"/>
                            <dxgext:ColumnDefinition Width="*"/>
                            
                        </dxgext:BandedViewBehavior.ColumnDefinitions>
                        <dxgext:BandedViewBehavior.RowDefinitions>
                            <dxgext:RowDefinition Height="Auto"/>
                            <dxgext:RowDefinition Height="Auto"/>
                         
                        </dxgext:BandedViewBehavior.RowDefinitions>
                        <dxgext:BandedViewBehavior.TemplatesContainer>
                            <dxgext:TemplatesContainer/>
                        </dxgext:BandedViewBehavior.TemplatesContainer>
                    </dxgext:BandedViewBehavior>
                </i:Interaction.Behaviors>
            </dxg:TableView>
        </dxg:GridControl.View>
        <dxg:GridControl.Columns>
            <dxg:GridColumn FieldName="Common" dxgext:BandedViewBehavior.ColumnSpan="2" />
            <dxg:GridColumn FieldName="First" dxgext:BandedViewBehavior.Row="1"/>
            <dxg:GridColumn FieldName="Second" dxgext:BandedViewBehavior.Row="1" dxgext:BandedViewBehavior.Column="1"/>
        </dxg:GridControl.Columns>
    </dxg:GridControl>

|  11    |   12  |
|1  | 2  | 3 |  4|

|       11       |        12     |
|1  | 2  | 3 | 4 |5  | 6  | 7 | 8|

 GridColumn columns_grafik = new GridColumn()
            {
                FieldName = i.ToString();
???                ColumnSpan=?
            };

GridColumn columns_grafik = new GridColumn()
            {
                FieldName = "Name"
            };
            columns_grafik.SetValue(BandedViewExtension.BandedViewBehavior.ColumnSpanProperty, 2);
            gridControl_grafik.Columns.Add(columns_grafik);
            GridColumn columns_grafik_1 = new GridColumn()
            {
                FieldName = "1"

            };
            columns_grafik_1.SetValue(BandedViewExtension.BandedViewBehavior.RowProperty, 1);
            gridControl_grafik.Columns.Add(columns_grafik_1);
            for (int j = 1; j <= 2; j++)
            {
                GridColumn columns_grafik3 = new GridColumn()
                {
                    FieldName = j.ToString()

                };
                columns_grafik3.SetValue(BandedViewExtension.BandedViewBehavior.RowProperty, 1);
                columns_grafik3.SetValue(BandedViewExtension.BandedViewBehavior.ColumnProperty, j);
                gridControl_grafik.Columns.Add(columns_grafik3);
            }

<dxlc:LayoutControl>
            <dxlc:LayoutGroup Header="Layout Group" View="GroupBox" IsCollapsible="True" FlowDirection="RightToLeft">
                <dxlc:LayoutGroup.Resources>
                    <Style TargetType="dxlc:GroupBoxButton">
                    </Style>
                </dxlc:LayoutGroup.Resources>
                <ListBox Height="246" HorizontalAlignment="Left" Margin="564,104,0,0" Name="listBox1" VerticalAlignment="Top" Width="211" />
            </dxlc:LayoutGroup>
        </dxlc:LayoutControl>

 <dxg:GridColumn FieldName="Common" dxgext:BandedViewBehavior.ColumnSpan="2">
                    
 </dxg:GridColumn>

<dxg:GridColumn FieldName="Common" dxgext:BandedViewBehavior.ColumnSpan="2" dxgext:BandedViewBehavior.IsBand="True">
                    <dxg:GridColumn.Header>
                        <DataTemplate>
                            <toolkit:Expander Height="Auto" HorizontalAlignment="Left" Name="expander1" VerticalAlignment="Top" Width="186" Header="Expander"
                          Grid.Column="1">
                                <Grid HorizontalAlignment="Stretch" Name="grid1" VerticalAlignment="Stretch" Width="182" >
                                    <ListBox Height="128" HorizontalAlignment="Left" Name="listBox1" VerticalAlignment="Top" Width="182">
                                    </ListBox>
                                </Grid>
                            </toolkit:Expander>
                        </DataTemplate>
                   </dxg:GridColumn.Header>
                </dxg:GridColumn>
                <dxg:GridColumn FieldName="First" dxgext:BandedViewBehavior.Row="1"/>
                <dxg:GridColumn FieldName="Second" dxgext:BandedViewBehavior.Row="1" dxgext:BandedViewBehavior.Column="1"/>
            </dxg:GridControl.Columns>

<ListBox Height="128" HorizontalAlignment="Left" Name="listBox_calendar" VerticalAlignment="Top" Width="182"
                             ItemsSource="{Binding}" DisplayMemberPath="First">
</ListBox>

  for (line=0; line<=6; line++)
    {
     listBox_calendar.Items.Add(line.ToString());//Получилось бы если мог обратится к свойству Items
    }

 private ArrayList  GetData()
        {
            ArrayList data = new ArrayList();
            data.Add("1");
            data.Add("2");
            return data;
        }

DataContext = GetData();

<DataTemplate x:Key="calendar">
            <toolkit:Expander Height="Auto" HorizontalAlignment="Right" Name="expander_calendar" 
                              VerticalAlignment="Top" Header="Expander"
                              Grid.Column="1">
                <Grid HorizontalAlignment="Stretch" Name="grid1">
                    <ListBox Height="100" HorizontalAlignment="Left"  Name="listBox2" 
                     VerticalAlignment="Top" Width="1200" ItemsSource="{Binding}">
                    </ListBox>
                </Grid>
            </toolkit:Expander>
        </DataTemplate>

Header="{StaticResource calendar}"

HeaderCustomizationAreaTemplate="{StaticResource calendar}"

 for (i = 0; i <= 20; i++)// количество столбцов
            {
             for (j = 0; j <= 50; j++)// количество столбцов
              {
                s=x*y....;// что-то считаем
               GridColumn columns_grafik = new GridColumn()
               {
                  FieldName = "n"+i.ToString()
               };
               gridControl_grafik.Columns.Add(columns_grafik);
             }
         }

   public class DataList : List<Data>
      {
         public DataList()
          {
          for (i = 0; i <= 20; i++)// количество столбцов
            {
             for (j = 0; j <= 50; j++)// количество столбцов
              {
                s=x*y....;// что-то считаем
               GridColumn columns_grafik = new GridColumn()
               {
                  FieldName = "n"+i.ToString()
               };
               gridControl_grafik.Columns.Add(columns_grafik);
             }
         }
          Data d = new Data();
          d.n1 = s;
          Add(d);
          }
.......
  public class Data
        {
            public string n1 { get; set; }
.....////Что в ручную все столбцы перечислять?
            public string n2 { get; set; }
        }
.......

     gridControl_grafik.DataContext = new DataList();