Highlight Filtering Results by using HTML-like text formatting in RadListView

Environment

Product Version Product Author
2020.1.113 RadListView for WinForms Nadya Karaivanova

Description

This tutorial demonstrates how to highlight text results both backcolor and forecolor when filtering in RadListView by using HTML-like text formatting approach.

highlight-filtering-results-with-html.png

Solution

First, I would like to note that HTML-like text formatting uses uses GDI+ to measure and render the text. You can find more information about text rendering here.

The desired text highlight effect can be achieved by subscribing to the VisualItemFormatting event that provides a convenient way for customizing the items appearance. In this event you have access to the ListViewDataItem via the VisualItem.Data property. Then, you can separate the text to a small parts by the searched symbol/s. Finally, you can use the HTML-like text formatting to apply a specific look of the text parts accordingly.

A full code snippet is illustrated below:


public RadForm1()
{
    InitializeComponent();
    this.radListView1.UseCompatibleTextRendering = true;

    radListView1.EnableFiltering = true;
    this.radTextBoxControl1.TextChanged += this.radTextBoxControl1_TextChanged;
    this.radListView1.VisualItemFormatting += this.RadListView1_VisualItemFormatting;
}

string searchedValue;
private void RadListView1_VisualItemFormatting(object sender, ListViewVisualItemEventArgs e)
{
    ListViewDataItem data = e.VisualItem.Data as ListViewDataItem;
    if (data != null && searchedValue != null)
    {
        string dataText = data.Text;
        if (dataText.Contains(searchedValue))
        {
            string firstPart = dataText.Substring(0, dataText.IndexOf(searchedValue));
            int startFormatting = dataText.IndexOf(searchedValue) + searchedValue.Length;
            string secondPart = dataText.Substring(startFormatting, dataText.Length - startFormatting);

            e.VisualItem.Text = String.Format(@"<html>" + firstPart + "<span style=\"color: white\"><span style=\"background-color:red\">" + searchedValue + "</span><span style=\"color: black\">" + secondPart) + "</span></html>";
        }
    }
}
private void radTextBoxControl1_TextChanged(object sender, EventArgs e)
{
    searchedValue = (sender as RadTextBoxControl).Text;
    if (searchedValue != null)
    {
        FilterDescriptor valueFilter = new FilterDescriptor(this.radListView1.DisplayMember, FilterOperator.Contains, searchedValue);
        this.radListView1.FilterDescriptors.Add(valueFilter);
    }
}



Public Class RadForm1
    Public Sub New()
        InitializeComponent()
        Me.RadListView1.UseCompatibleTextRendering = True
        RadListView1.EnableFiltering = True
        AddHandler Me.RadTextBoxControl1.TextChanged, AddressOf RadTextBoxControl1_TextChanged_1
        AddHandler Me.RadListView1.VisualItemFormatting, AddressOf Me.RadListView1_VisualItemFormatting
    End Sub

    Private searchedValue As String
    Private Sub RadListView1_VisualItemFormatting(ByVal sender As Object, ByVal e As ListViewVisualItemEventArgs)
        Dim data As ListViewDataItem = TryCast(e.VisualItem.Data, ListViewDataItem)

        If data IsNot Nothing AndAlso searchedValue IsNot Nothing Then
            Dim dataText As String = data.Text

            If dataText.Contains(searchedValue) Then
                Dim firstPart As String = dataText.Substring(0, dataText.IndexOf(searchedValue))
                Dim startFormatting As Integer = dataText.IndexOf(searchedValue) + searchedValue.Length
                Dim secondPart As String = dataText.Substring(startFormatting, dataText.Length - startFormatting)
                e.VisualItem.Text = String.Format("<html>" & firstPart & "<span style=""color: white""><span style=""background-color:red"">" & searchedValue & "</span><span style=""color: black"">" & secondPart) & "</span></html>"
            End If
        End If
    End Sub

    Private Sub RadTextBoxControl1_TextChanged_1(sender As Object, e As EventArgs) Handles RadTextBoxControl1.TextChanged
        searchedValue = (TryCast(sender, RadTextBoxControl)).Text
        If searchedValue IsNot Nothing Then
            Dim valueFilter As FilterDescriptor = New FilterDescriptor(Me.RadListView1.DisplayMember, FilterOperator.Contains, searchedValue)
            Me.RadListView1.FilterDescriptors.Add(valueFilter)
        End If
    End Sub
End Class

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