In This Topic
Expression Editor provides various built-in functions to create expressions for your applications. Furthermore, it allows you to define custom functions according to your application’s requirement. The AddFunction method of C1ExpressionEditor class allows you to add custom functions to Expression Editor. This custom function gets added to the ExpressionEditor engine and is accessible at runtime by C1ExpreesionEditor for performing calculations.
The following image shows a custom function used in the ExpressionEditor control.
The following code demonstrates how a custom function is created and added to the Expression Editor panel:
Public NotInheritable Partial Class MainPage
Inherits Page
Public Sub New()
Me.InitializeComponent()
ExpressionPanel.ExpressionEditor = ExpressionEditor
Dim factItem As ExpressionItem = New ExpressionItem("Factorial", "Factorial()",
"Returns the product of an integer and all the integers below it.",
ItemType.MathFuncs)
factItem.Arguments.Add(New Argument("number", GetType(System.Double)))
ExpressionEditor.AddFunction(factItem, AddressOf Factorial, 1, 1)
End Sub
Private Function Factorial(ByVal list As List(Of Object)) As Object
Dim items As List(Of Object) = New List(Of Object)()
items = items.Concat(list).ToList()
Dim i, number As Integer, fact As Integer = 1
number = Convert.ToInt32(items(0))
For i = 1 To number
fact = fact * i
Next
Return fact
End Function
Private Sub ExpressionEditor_ExpressionChanged(ByVal sender As Object, ByVal e As EventArgs)
If Not ExpressionEditor.IsValid Then
Result.Text = ""
Else
Result.Text = ExpressionEditor.Evaluate()?.ToString()
End If
End Sub
End Class
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
ExpressionPanel.ExpressionEditor = ExpressionEditor;
ExpressionItem factItem = new ExpressionItem("Factorial", "Factorial()",
"Returns the product of an integer and all the integers below it.",
ItemType.MathFuncs);
factItem.Arguments.Add(new Argument("number", typeof(System.Double)));
ExpressionEditor.AddFunction(factItem, Factorial, 1, 1);
}
private object Factorial(List<object> list)
{
List<object> items = new List<object>();
items = items.Concat(list).ToList();
int i, fact = 1, number;
number = Convert.ToInt32(items[0]);
for (i = 1; i <= number; i++)
{
fact = fact * i;
}
return fact;
}
private void ExpressionEditor_ExpressionChanged(object sender, EventArgs e)
{
if (!ExpressionEditor.IsValid)
{
Result.Text = "";
}
else
{
Result.Text = ExpressionEditor.Evaluate()?.ToString();
}
}
}
