if I run the following code

<%@ Page Language = "C#"%>

<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>

<script runat="server">
	public class MonitorViewer
	{
		private double yieldValue;
		private int pnFirstOk;
		private int pnFirstKo;
		private int pnTotalPass;
		private string period;
		
		public MonitorViewer() {}
		
		public double YieldValue {
			get { return yieldValue; }
			set { yieldValue = value; }
		}
		
		public int PnFirstOk {
			get { return pnFirstOk; }
			set { pnFirstOk = value; }
		}
		
		public int PnFirstKo {
			get { return pnFirstKo; }
			set { pnFirstKo = value; }
		}
		
		public int PnTotalPass {
			get { return pnTotalPass; }
			set { pnTotalPass = value; }
		}
		
		public string Period {
			get { return period; }
			set { period = value; }
		}
	}
	
	public object[] DataValue () {
			IList<MonitorViewer> listItems = new List<MonitorViewer>();
			MonitorViewer monitorViewer1 = new MonitorViewer();
			monitorViewer1.YieldValue = Double.Parse("95,97");
			monitorViewer1.Period= "30/03/12 - 20/04/12";
			monitorViewer1.PnFirstOk = 7507;
			monitorViewer1.PnFirstKo = 315;
			monitorViewer1.PnTotalPass = 7994;
			
			MonitorViewer monitorViewer2 = new MonitorViewer();
			monitorViewer2.YieldValue = Double.Parse("96,68");
			monitorViewer2.Period= "20/04/12 - 12/05/12";
			monitorViewer2.PnFirstOk = 5995;
			monitorViewer2.PnFirstKo = 206;
			monitorViewer2.PnTotalPass = 6504;
			
			MonitorViewer monitorViewer3 = new MonitorViewer();
			monitorViewer3.YieldValue = Double.Parse("95,91");
			monitorViewer3.Period= "12/05/12 - 03/06/12";
			monitorViewer3.PnFirstOk = 9732;
			monitorViewer3.PnFirstKo = 415;
			monitorViewer3.PnTotalPass = 10209;
			
			MonitorViewer monitorViewer4 = new MonitorViewer();
			monitorViewer4.YieldValue = Double.Parse("96,09");
			monitorViewer4.Period= "03/06/12 - 24/06/12";
			monitorViewer4.PnFirstOk = 6710;
			monitorViewer4.PnFirstKo = 273;
			monitorViewer4.PnTotalPass = 7309;
			
			MonitorViewer monitorViewer5 = new MonitorViewer();
			monitorViewer5.YieldValue = Double.Parse("96,29");
			monitorViewer5.Period= "24/06/12 - 16/07/12";
			monitorViewer5.PnFirstOk = 1922;
			monitorViewer5.PnFirstKo = 74;
			monitorViewer5.PnTotalPass = 2021;
			
			MonitorViewer monitorViewer6 = new MonitorViewer();
			monitorViewer6.YieldValue = Double.Parse("0,0");
			monitorViewer6.Period= "16/07/12 - 07/08/12";
			monitorViewer6.PnFirstOk = 0;
			monitorViewer6.PnFirstKo = 0;
			monitorViewer6.PnTotalPass = 0;
			
			MonitorViewer monitorViewer7 = new MonitorViewer();
			monitorViewer7.YieldValue = Double.Parse("0,0");
			monitorViewer7.Period= "07/08/12 - 28/08/12";
			monitorViewer7.PnFirstOk = 0;
			monitorViewer7.PnFirstKo = 0;
			monitorViewer7.PnTotalPass = 0;
			
			listItems.Add(monitorViewer1);
			listItems.Add(monitorViewer2);
			listItems.Add(monitorViewer3);
			listItems.Add(monitorViewer4);
			listItems.Add(monitorViewer5);
			listItems.Add(monitorViewer6);
			listItems.Add(monitorViewer7);
			
			object[] periodArray = new object[listItems.Count];
			for (int i = 0;i < listItems.Count;i++) {
				MonitorViewer monitorViewer = listItems[i];
				object[] itemArray = new object[]{monitorViewer.YieldValue,monitorViewer.Period};
				
				periodArray[i] = itemArray;
			}
			return periodArray;
		}
		
		public void Page_Load() {

	        var store = this.yieldChart.GetStore();
	        store.DataSource = DataValue();
	        store.DataBind();
		}
		
		protected void ExtractData(object sender, DirectEventArgs e) {
		}
</script>

<body>
	<form Method=post Runat="server">
		<ext:ResourceManager Id="resourceManager" runat="server" />
			<h3>Example</h3>
			<br/>
			<ext:Button ID="btnSearch" Text="Search" runat="server" Hidden="false" Icon="Magnifier" >
				<DirectEvents>
					<Click OnEvent="ExtractData">
						<EventMask ShowMask="true" MinDelay="100"/>
					</Click>
				</DirectEvents>
			</ext:Button>
			<br/>
			<ext:Panel runat="server" Height="200" Layout="FitLayout" MarginSpec="0 0 3 0">
			    <Items>
			        <ext:Chart 
			            ID="yieldChart" 
			            runat="server" 
			            Flex="1" 
			            Shadow="true" 
			            Animate="true">
						<Store>
                        <ext:Store runat="server">
                            <Model>
			                        <ext:Model runat="server">
			                            <Fields>
											<ext:ModelField Name="yield"  />
											<ext:ModelField Name="period"  />
											<ext:ModelField Name="pnFirstPass" Type="Int" />
											<ext:ModelField Name="pnFirstFail"  Type="Int" />
											<ext:ModelField Name="pnTotalPass" Type="Int" />
			                            </Fields>
			                        </ext:Model>
                            </Model>
                        </ext:Store>
						</Store>
			            <Axes>
			                <ext:NumericAxis Position="Left" Fields="yield" Minimum="0" />
			                <ext:CategoryAxis Position="Bottom" Fields="period">
			                    <Label Font="9px Arial">
			                        <Rotate Degrees="270" />
			                        <Renderer Handler="return Ext.String.ellipsis(value, 15, false);" />
			                    </Label>
			                </ext:CategoryAxis>
			            </Axes> 
			
			            <Series>
			                <ext:ColumnSeries 
			                    Axis="Left" 
			                    Highlight="true" 
			                    XField="Period" 
			                    YField="yield">
			                    <Style Fill="#456d9f" />
			                    <HighlightConfig Fill="#a2b5ca" />
			                    <Label 
			                        Contrast="true" 
			                        Display="InsideEnd" 
			                        Field="Period" 
			                        Color="#000" 
			                        Orientation="Vertical" 
			                        TextAnchor="middle"
			                        />
			                </ext:ColumnSeries>
			            </Series>
			        </ext:Chart>
                    </Items>
                </ext:Panel>
			    </Items>
			</ext:Panel>
    </form>
</Body>
</Html>
I see this Click image for larger version. 

Name:	example.JPG 
Views:	53 
Size:	30.7 KB 
ID:	4701

If I change the part of code as below

		public void Page_Load() {

		}
		
		protected void ExtractData(object sender, DirectEventArgs e) {
	           var store = this.yieldChart.GetStore();
	           store.DataSource = DataValue();
	           store.DataBind();
		}
I see this Click image for larger version. 

Name:	example1.JPG 
Views:	59 
Size:	22.3 KB 
ID:	4702
after clicked on button search

Thank you so much