EditControl
├── Editor Area - Main text editing surface
│   ├── Line Numbers (optional)
│   ├── Folding Indicators (optional)
│   └── Text Content with Syntax Highlighting
├── Context Menu - Right-click operations
├── Status Bar (optional) - Position and mode info
└── IntelliSense Popup - Auto-completion suggestions

<Window x:Class="CodeEditorApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:syncfusion="http://schemas.syncfusion.com/wpf">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        
        <!-- Toolbar -->
        <ToolBar Grid.Row="0">
            <Button Content="Open" Click="OpenFile_Click"/>
            <Button Content="Save" Click="SaveFile_Click"/>
            <Separator/>
            <ComboBox Name="languageComboBox" 
                      SelectionChanged="Language_Changed"
                      Width="120">
                <ComboBoxItem Content="C#" Tag="CSharp"/>
                <ComboBoxItem Content="Visual Basic" Tag="VB"/>
                <ComboBoxItem Content="XAML" Tag="XAML"/>
                <ComboBoxItem Content="XML" Tag="XML"/>
            </ComboBox>
        </ToolBar>
        
        <!-- Syntax Editor -->
        <syncfusion:EditControl Name="editControl" 
                                Grid.Row="1"
                                DocumentLanguage="CSharp"
                                ShowLineNumber="True"
                                EnableOutlining="True"
                                EnableIntellisense="True"
                                Background="White"
                                FontSize="12"
                                FontFamily="Consolas"/>
    </Grid>
</Window>

using Syncfusion.Windows.Edit;
using Microsoft.Win32;
using System.IO;
using System.Windows;

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        
        // Set initial language
        editControl.DocumentLanguage = Languages.CSharp;
        languageComboBox.SelectedIndex = 0;
    }
    
    private void OpenFile_Click(object sender, RoutedEventArgs e)
    {
        OpenFileDialog dialog = new OpenFileDialog
        {
            Filter = "C# Files (*.cs)|*.cs|VB Files (*.vb)|*.vb|XAML Files (*.xaml)|*.xaml|All Files (*.*)|*.*"
        };
        
        if (dialog.ShowDialog() == true)
        {
            editControl.Load(dialog.FileName);
            
            // Auto-detect language from extension
            string ext = Path.GetExtension(dialog.FileName).ToLower();
            switch (ext)
            {
                case ".cs":
                    editControl.DocumentLanguage = Languages.CSharp;
                    break;
                case ".vb":
                    editControl.DocumentLanguage = Languages.VB;
                    break;
                case ".xaml":
                    editControl.DocumentLanguage = Languages.XAML;
                    break;
                case ".xml":
                    editControl.DocumentLanguage = Languages.XML;
                    break;
            }
        }
    }
    
    private void SaveFile_Click(object sender, RoutedEventArgs e)
    {
        SaveFileDialog dialog = new SaveFileDialog
        {
            Filter = "C# Files (*.cs)|*.cs|VB Files (*.vb)|*.vb|XAML Files (*.xaml)|*.xaml|All Files (*.*)|*.*"
        };
        
        if (dialog.ShowDialog() == true)
        {
            editControl.Save(dialog.FileName);
        }
    }
    
    private void Language_Changed(object sender, SelectionChangedEventArgs e)
    {
        if (editControl == null) return;
        
        var selected = (ComboBoxItem)languageComboBox.SelectedItem;
        string language = selected.Tag.ToString();
        
        switch (language)
        {
            case "CSharp":
                editControl.DocumentLanguage = Languages.CSharp;
                break;
            case "VB":
                editControl.DocumentLanguage = Languages.VB;
                break;
            case "XAML":
                editControl.DocumentLanguage = Languages.XAML;
                break;
            case "XML":
                editControl.DocumentLanguage = Languages.XML;
                break;
        }
    }
}

// Load file with specific encoding
editControl.Load("path/to/file.cs", Encoding.UTF8);

// Save with encoding
editControl.Save("path/to/output.cs", Encoding.UTF8);

// Load from stream
using (FileStream stream = new FileStream("file.cs", FileMode.Open))
{
    editControl.Load(stream, Encoding.UTF8);
}

// Save to stream
using (FileStream stream = new FileStream("output.cs", FileMode.Create))
{
    editControl.Save(stream, Encoding.UTF8);
}

// Enable IntelliSense in Custom mode
editControl.EnableIntellisense = true;
editControl.IntellisenseMode = IntellisenseMode.Custom;

// Business object must implement IIntellisenseItem
public class MyIntellisenseItem : IIntellisenseItem
{
    public ImageSource Icon { get; set; }
    public string Text { get; set; }
    public IEnumerable<IIntellisenseItem> NestedItems { get; set; }
}

// Build custom items collection and assign to IntellisenseCustomItemsSource
var customItems = new ObservableCollection<MyIntellisenseItem>
{
    new MyIntellisenseItem { Text = "CustomMethod" },
    new MyIntellisenseItem { Text = "CustomProperty" },
    new MyIntellisenseItem { Text = "Console" }
};
editControl.IntellisenseCustomItemsSource = customItems;

// Handle IntelliSenseBoxOpening event to filter items at runtime
editControl.IntelliSenseBoxOpening += (s, e) =>
{
    // e.ItemsSource contains current items; set e.Cancel = true to suppress popup
    if (string.IsNullOrEmpty(editControl.Text))
        e.Cancel = true;
};

// Simple find
FindResult result = editControl.FindText("SearchTerm", 
    FindOptions.MatchCase | FindOptions.WholeWord);

if (result != null)
{
    Console.WriteLine($"Found at line {result.LineNumber}");
}

// Find with regex
FindResult regexResult = editControl.FindText(@"\d{3}-\d{4}", 
    FindOptions.UseRegularExpressions);

// Replace all occurrences
int replacedCount = editControl.ReplaceAll("oldText", "newText", 
    FindOptions.MatchCase);

// Replace with confirmation
while (editControl.FindNext("oldText", FindOptions.None))
{
    var dialogResult = MessageBox.Show("Replace this occurrence?", 
        "Confirm", MessageBoxButton.YesNoCancel);
    
    if (dialogResult == MessageBoxResult.Yes)
        editControl.SelectedText = "newText";
    else if (dialogResult == MessageBoxResult.Cancel)
        break;
}

<!-- Define formats in XAML Resources -->
<syncfusion:FormatsCollection x:Key="myLangFormats">
    <syncfusion:EditFormats Foreground="Blue"  FormatName="KeywordFormat"/>
    <syncfusion:EditFormats Foreground="Green" FormatName="CommentFormat"/>
    <syncfusion:EditFormats Foreground="Brown" FormatName="StringFormat"/>
</syncfusion:FormatsCollection>

<!-- Define lexems in XAML Resources -->
<syncfusion:LexemCollection x:Key="myLangLexems">
    <syncfusion:Lexem StartText="function" LexemType="Keyword"  FormatName="KeywordFormat" ContainsEndText="False" IsMultiline="False"/>
    <syncfusion:Lexem StartText="if"       LexemType="Keyword"  FormatName="KeywordFormat" ContainsEndText="False" IsMultiline="False"/>
    <syncfusion:Lexem StartText="while"    LexemType="Keyword"  FormatName="KeywordFormat" ContainsEndText="False" IsMultiline="False"/>
    <syncfusion:Lexem StartText="//"       EndText="\r\n" LexemType="Comment" FormatName="CommentFormat" ContainsEndText="True" IsMultiline="False"/>
    <syncfusion:Lexem StartText="&quot;"  EndText="&quot;" LexemType="Literals" FormatName="StringFormat" ContainsEndText="True" IsMultiline="False"/>
</syncfusion:LexemCollection>

// Create custom language class inheriting ProceduralLanguageBase
public class MyLanguage : ProceduralLanguageBase
{
    public MyLanguage(EditControl control) : base(control)
    {
        Name = "MyLanguage";
        FileExtension = "mylang";
        ApplyColoring = true;
        SupportsOutlining = false;
        SupportsIntellisense = false;
        TextForeground = Brushes.Black;
    }
}

// Wire up resources and apply the custom language
EditControl editControl = new EditControl();
editControl.DocumentLanguage = Languages.Custom;

MyLanguage customLanguage = new MyLanguage(editControl);
customLanguage.Lexem    = Application.Current.Resources["myLangLexems"]   as LexemCollection;
customLanguage.Formats  = Application.Current.Resources["myLangFormats"]  as FormatsCollection;
editControl.CustomLanguage = customLanguage;

// Enable outlining
editControl.EnableOutlining = true;

// Collapse all regions
editControl.CollapseAll();

// Expand all regions
editControl.ExpandAll();

// Toggle specific region
editControl.ToggleOutlining(lineNumber);

// Programmatically add folding region
editControl.AddFoldingRegion(startLine, endLine, "Region Name");

// Handle outlining events
editControl.OutlineCollapsed += (s, e) =>
{
    Console.WriteLine($"Collapsed region at line {e.StartLine}");
};