Spread Windows Forms 17
Spread Windows Forms 17.0 Product Documentation / Developer's Guide / Formulas in Cells / Creating and Using External Variable / Using External Variables with Text Box Control
In This Topic
    Using External Variables with Text Box Control
    In This Topic

    The following example code shows how to create and use external variables with the standard textbox control.

    In the example:

    C#
    Copy Code 
    // Creating and defining the external variable
public class TextBoxExternalVariable : ExternalVariable
{
    private TextBox _textBox;
    private bool _asInput;
    public TextBoxExternalVariable(TextBox textBox, bool asInput)
    {
        _textBox = textBox;
        if (asInput)
        {
            textBox.TextChanged += TextBox_TextChanged;
        }
    }
    private void TextBox_TextChanged(object sender, EventArgs e)
    {
        Dirty();
    }
   
    protected override bool OnDirtying()
    {
        return !_asInput;
    }
  
    protected override void OnDirtied()
    {
        Refresh();
    }
   
    protected override void EvaluateCore(IEvaluationContext context,
     IValue result)
    {
        string text = _textBox.Text;
        if (!string.IsNullOrEmpty(text) && double.TryParse(text,
             out double dblValue))
        {
            result.SetValue(dblValue);
        }
        else
        {
            result.SetValue(text);
        }
    }
   
    public void Refresh()
    {
        if (!_asInput)
        {
            _textBox.Text = this.Value.GetText();
        }
    }
} 
// Using the external variable with text box control
private void Form2_Load(object sender, EventArgs e)
{
 var workbook = fpSpread1.AsWorkbook();
 var activeSheet = workbook.ActiveSheet;
 activeSheet.Cells["A1"].Value = "Factor";
 activeSheet.Cells["B1"].Value = 2;
   
 // Adding Ext. Variable - x referring to textbox1
 workbook.Names.AddExternalVariable("x",
 new TextBoxExternalVariable(textBox1, true));
   
 // Adding Ext. Variable "y" referring to textbox2 with formula "Sheet1!B1 * x"
 var extVariable2 = new TextBoxExternalVariable(textBox2, false);
 workbook.Names.AddExternalVariable("y", extVariable2, "Sheet1!B1 * x");
 extVariable2.Refresh();
}

    VB
    Copy Code 
    'Creating and defining the external variable
Public Class TextBoxExternalVariable Inherits ExternalVariable
Private _textBox As TextBox
Private _asInput As Boolean
Public Sub New(ByVal textBox As TextBox, ByVal asInput As Boolean)
_textBox = textBox
If asInput Then
textBox.TextChanged += AddressOf TextBox_TextChanged
End If
End Sub
Private Sub TextBox_TextChanged(ByVal sender As Object, ByVal e As EventArgs)
Dirty()
End Sub
Protected Overrides Function OnDirtying() As Boolean
Return Not _asInput
End Function
Protected Overrides Sub OnDirtied()
Refresh()
End Sub
Protected Overrides Sub EvaluateCore(ByVal context As IEvaluationContext, ByVal result As IValue)
Dim text As String = _textBox.Text
Dim dblValue As Double = Nothing
If Not String.IsNullOrEmpty(text) AndAlso Double.TryParse(text, dblValue) Then
result.SetValue(dblValue)
Else
result.SetValue(text)
End If
End Sub
Public Sub Refresh()
If Not _asInput Then
_textBox.Text = Me.Value.GetText()
End If
End Sub
End Class    

'Using the external variable with text box control
Private Sub Form2_Load(ByVal sender As Object, ByVal e As EventArgs)
Dim workbook = fpSpread1.AsWorkbook()
Dim activeSheet = workbook.ActiveSheet
activeSheet.Cells("A1").Value = "Factor"
activeSheet.Cells("B1").Value = 2
workbook.Names.AddExternalVariable("x", New TextBoxExternalVariable(textBox1, True))
Dim extVariable2 = New TextBoxExternalVariable(textBox2, False)
workbook.Names.AddExternalVariable("y", extVariable2, "Sheet1!B1 * x")
extVariable2.Refresh()
End Sub