# Key Hints for Chart WPF
## Content
The following top tips for Chart for WPF and Silverlight will help you when you use the C1Chart control.
**Tip 1: Use the BeginUpdate()/EndUpdate() methods to improve performance**
This improves performance since the redrawing occurs only once after a call of the **EndUpdate()** method.
For example:
```vbnet
' start update
C1Chart1.BeginUpdate()
Dim nser As Integer = 10, npts As Integer = 100
For iser As Integer = 1 To nser
' create data arrays
Dim x(npts - 1) As Double, y(npts - 1) As Double
For ipt As Integer = 0 To npts - 1
x(ipt) = ipt
y(ipt) = (1 + 0.05 * iser) * Math.Sin(0.1 * ipt + 0.1 * iser)
Next
' create data series and add it to the chart
Dim ds = New XYDataSeries()
ds.XValuesSource = x
ds.ValuesSource = y
C1Chart1.Data.Children.Add(ds)
Next
' set chart type
C1Chart1.ChartType = ChartType.Line
' finish update
C1Chart1.EndUpdate()
```
```csharp
// start update
c1Chart1.BeginUpdate();
int nser = 10, npts = 100;
for (int iser = 0; iser < nser; iser++)
{
// create data arrays
double[] x = new double[npts], y = new double[npts];
for (int ipt = 0; ipt < npts; ipt++)
{
x[ipt] = ipt;
y[ipt] = (1 + 0.05 * iser) * Math.Sin(0.1 * ipt + 0.1 * iser);
}
// create data series and add it to the chart
XYDataSeries ds = new XYDataSeries();
ds.XValuesSource = x; ds.ValuesSource = y;
c1Chart1.Data.Children.Add(ds);
}
// set chart type
c1Chart1.ChartType = ChartType.Line;
// finish update
c1Chart1.EndUpdate();
```
**Tip 2: Use the Line or Area type chart for large data arrays**
The line and area charts provide the best performance when you have a lots of data values.
To get better performance, enable built-in optimization for large data by setting the attached property, **LineAreaOptions.OptimizationRadius**. For example:
```vbnet
LineAreaOptions.SetOptimizationRadius(C1Chart1, 1.0)
```
```csharp
LineAreaOptions.SetOptimizationRadius(c1Chart1, 1.0);
```
It's recommended you use small values 1.0 - 2.0 as radius. A larger value may affect the accuracy of the plot.
**Tip 3: Update the appearance and behavior of a plot element using the DataSeries.PlotElementLoaded event**
When any plot element (bar,column,pie, etc) is loaded it fires the [PlotElementLoaded](/componentone/api/wpf/online-chart/dotnet-framework-api/C1.WPF.C1Chart.4.6.2/C1.WPF.C1Chart.DataSeries.PlotElementLoaded.html) event. During this event you have access to the plot element properties as well as to the corresponding data point.
The following code sets the colors of points depending on its y-value. For example:
```vbnet
' create data arrays
Dim npts As Integer = 100
Dim x(npts - 1) As Double, y(npts - 1) As Double
For ipt As Integer = 0 To npts - 1
x(ipt) = ipt
y(ipt) = Math.Sin(0.1 * ipt)
Next
' create data series
Dim ds = New XYDataSeries()
ds.XValuesSource = x
ds.ValuesSource = y
' set event handler
AddHandler ds.PlotElementLoaded, AddressOf PlotElement_Loaded
' add data series to the chart
C1Chart1.Data.Children.Add(ds)
' set chart type
C1Chart1.ChartType = ChartType.LineSymbols
...
' event handler
Sub PlotElement_Loaded(ByVal sender As Object, ByVal args As EventArgs)
Dim pe = CType(sender, PlotElement)
If Not TypeOf pe Is Lines Then
Dim dp As DataPoint = pe.DataPoint
' normalized y-value(from 0 to 1)
Dim nval As Double = 0.5 * (dp.Value + 1)
' fill from blue(-1) to red(+1)
pe.Fill = New SolidColorBrush(Color.FromRgb(CByte(255 * nval), _
0, CByte(255 * (1 - nval))))
End If
End Sub
```
```csharp
// create data arrays
int npts = 100;
double[] x = new double[npts], y = new double[npts];
for (int ipt = 0; ipt < npts; ipt++)
{
x[ipt] = ipt;
y[ipt] = Math.Sin(0.1 * ipt);
}
// create data series
XYDataSeries ds = new XYDataSeries();
ds.XValuesSource = x; ds.ValuesSource = y;
// set event handler
ds.PlotElementLoaded += (s, e) =>
{
PlotElement pe = (PlotElement)s;
if (!(pe is Lines)) // skip lines
{
DataPoint dp = pe.DataPoint;
// normalized y-value(from 0 to 1)
double nval = 0.5*(dp.Value + 1);
// fill from blue(-1) to red(+1)
pe.Fill = new SolidColorBrush(
Color.FromRgb((byte)(255 * nval), 0, (byte)(255 * (1-nval))));
}
};
// add data series to the chart
c1Chart1.Data.Children.Add(ds);
// set chart type
c1Chart1.ChartType = ChartType.LineSymbols;
```
**Tip 4: Data point labels and tooltips**
To create a data point label or tooltip, you should set the data template for the PointLabelTemplate or PointTooltipTemplate property.
The following sample code shows the index for each data point.
```xml
```
**Tip 5: Save chart as image**
The following method saves chart image as png-file.
```vbnet
Sub Using stm = System.IO.File.Create(fileName)
c1Chart1.SaveImage(stm, ImageFormat.Png)
End Using
```
```csharp
using (var stm = System.IO.File.Create(fileName))
{
c1Chart1.SaveImage(stm, ImageFormat.Png);
}
```
**Tip 6: Printing chart**
The following code prints the specified chart on the default printer with the default settings. For example:
```vbnet
Dim pd = New PrintDialog()
pd.PrintVisual(C1Chart1, "chart")
```
```csharp
new PrintDialog().PrintVisual(c1Chart1, "chart");
```
**Tip 7: Mixing Cartesian chart types**
You can easily mix different chart types on the same Cartesian plot using the ChartType property.
The following code creates three data series: the first is area, the second is step, and the third has the default chart type (line).
```vbnet
Dim nser As Integer = 3, npts As Integer = 25
For iser As Integer = 1 To nser
' create data arrays
Dim x(npts - 1) As Double, y(npts - 1) As Double
For ipt As Integer = 0 To npts - 1
x(ipt) = ipt
y(ipt) = (1 + 0.05 * iser) * Math.Sin(0.1 * ipt + 0.1 * iser)
Next
' create data series and add it to the chart
Dim ds = New XYDataSeries()
ds.XValuesSource = x
ds.ValuesSource = y
C1Chart1.Data.Children.Add(ds)
Next
'default chart type
C1Chart1.ChartType = ChartType.Line
' 1st series
C1Chart1.Data.Children(0).ChartType = ChartType.Area
' 2nd series
C1Chart1.Data.Children(1).ChartType = ChartType.Step
```
```csharp
int nser = 3, npts = 25;
for (int iser = 0; iser < nser; iser++)
{
// create data arrays
double[] x = new double[npts], y = new double[npts];
for (int ipt = 0; ipt < npts; ipt++)
{
x[ipt] = ipt;
y[ipt] = (1 + 0.05 * iser) * Math.Sin(0.1 * ipt + 0.1 * iser);
}
// create data series and add it to the chart
XYDataSeries ds = new XYDataSeries();
ds.XValuesSource = x; ds.ValuesSource = y;
c1Chart1.Data.Children.Add(ds);
}
//default chart type
c1Chart1.ChartType = ChartType.Line;
// 1st series
c1Chart1.Data.Children[0].ChartType = ChartType.Area;
// 2nd series
c1Chart1.Data.Children[1].ChartType = ChartType.Step;
```
## See Also
[XAML Quick Reference](/componentone/docs/wpf/online-chart/overview/getting-started/xaml-quick-reference)