Custom labels text

Updated over 6 months ago

RadChartView allows you to easily change the axes labels text by using a custom format provider class. This class must implement the IFormatProvider and ICustomFormatter interfaces. The key point in this class is that the Format method is called for each label and its "arg" parameter contains the current label text. The returned value will represent the new label.

Example 1: Changing the labels' texts to more human readable ones

Label Format

C#

public class MyFormatProvider : IFormatProvider, ICustomFormatter
{
    public object GetFormat(Type formatType)
    {
        return this;
    }
    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        string s = arg.ToString();
        switch (s)
        {
            case "0":
                return "0 seconds";
            case "30":
                return "1/2 min";
            case "60":
                return "1 min";
            case "90":
                return "90 seconds";
        }
        return null;
    }
}

VB.NET

Class MyFormatProvider
    Implements IFormatProvider
    Implements ICustomFormatter
    Public Function GetFormat(formatType As Type) As Object Implements IFormatProvider.GetFormat
        Return Me
    End Function
    Public Function Format(format__1 As String, arg As Object, formatProvider As IFormatProvider) As String Implements ICustomFormatter.Format
        Dim s As String = arg.ToString()
        Select Case s
            Case "0"
                Return "0 seconds"
            Case "30"
                Return "1/2 min"
            Case "60"
                Return "1 min"
            Case "90"
                Return "90 seconds"
        End Select
        Return Nothing
    End Function
End Class

Then you can just change the horizontal axis LabelFormatProvider by using the corresponding property.

Assign Format Provider

C#

LinearAxis horizontalAxis = radChartView1.Axes.Get<LinearAxis>(0);
horizontalAxis.LabelFormatProvider = new MyFormatProvider();

VB.NET

Dim horizontalAxis As LinearAxis = RadChartView1.Axes.[Get](Of LinearAxis)(0)
horizontalAxis.LabelFormatProvider = New MyFormatProvider()

Figure 1: Format Provider

Example 2: Showing the date part of a label only on day changes

DateTime Format Provider

C#

public class DateTimeFormatProvider : IFormatProvider, ICustomFormatter
{
    public object GetFormat(Type formatType)
    {
        return this;
    }
    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        DateTime val = (DateTime)arg;
        if (val.Hour == 0)
        {
            return val.ToShortDateString();
        }
        else
        {
            return val.ToString("H\\h");
        }
    }
}

VB.NET

Class DateTimeFormatProvider
    Implements IFormatProvider
    Implements ICustomFormatter
    Public Function GetFormat(formatType As Type) As Object Implements IFormatProvider.GetFormat
        Return Me
    End Function
    Public Function Format(format__1 As String, arg As Object, formatProvider As IFormatProvider) As String Implements ICustomFormatter.Format
        Dim val As DateTime = DirectCast(arg, DateTime)
        If val.Hour = 0 Then
            Return val.ToShortDateString()
        Else
            Return val.ToString("H\h")
        End If
    End Function
End Class

Again you can just change the horizontal axis LabelFormatProvider by using the corresponding property.

Assign DateTime Format Provider

C#

DateTimeContinuousAxis dateTimeAxis = new DateTimeContinuousAxis();
dateTimeAxis.LabelFormatProvider = new DateTimeFormatProvider();

VB.NET

Dim dateTimeAxis As New DateTimeContinuousAxis()
dateTimeAxis.LabelFormatProvider = New DateTimeFormatProvider()

Figure 2: DateTime Format Provider

The above provider implementation is applicable only to axes working with DateTime objects ( DateTimeContinuousAxis and DateTimeCategoricalAxis ).

See Also

• Series Types
• Axes