DataTableReaderListener.cs

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using System.ComponentModel;
 
namespace System.Data;
 
internal sealed class DataTableReaderListener
{
    private DataTable _currentDataTable;
 
    private bool _isSubscribed;
 
    private readonly WeakReference _readerWeak;
 
    internal DataTableReaderListener(DataTableReader reader)
    {
        if (reader == null)
        {
            throw ExceptionBuilder.ArgumentNull("DataTableReader");
        }
        if (_currentDataTable != null)
        {
            UnSubscribeEvents();
        }
        _readerWeak = new WeakReference(reader);
        _currentDataTable = reader.CurrentDataTable;
        if (_currentDataTable != null)
        {
            SubscribeEvents();
        }
    }
 
    internal void CleanUp()
    {
        UnSubscribeEvents();
    }
 
    internal void UpdataTable(DataTable datatable)
    {
        if (datatable == null)
        {
            throw ExceptionBuilder.ArgumentNull("DataTable");
        }
        UnSubscribeEvents();
        _currentDataTable = datatable;
        SubscribeEvents();
    }
 
    private void SubscribeEvents()
    {
        if (_currentDataTable != null && !_isSubscribed)
        {
            _currentDataTable.Columns.ColumnPropertyChanged += SchemaChanged;
            _currentDataTable.Columns.CollectionChanged += SchemaChanged;
            _currentDataTable.RowChanged += DataChanged;
            _currentDataTable.RowDeleted += DataChanged;
            _currentDataTable.TableCleared += DataTableCleared;
            _isSubscribed = true;
        }
    }
 
    private void UnSubscribeEvents()
    {
        if (_currentDataTable != null && _isSubscribed)
        {
            _currentDataTable.Columns.ColumnPropertyChanged -= SchemaChanged;
            _currentDataTable.Columns.CollectionChanged -= SchemaChanged;
            _currentDataTable.RowChanged -= DataChanged;
            _currentDataTable.RowDeleted -= DataChanged;
            _currentDataTable.TableCleared -= DataTableCleared;
            _isSubscribed = false;
        }
    }
 
    private void DataTableCleared(object sender, DataTableClearEventArgs e)
    {
        DataTableReader dataTableReader = (DataTableReader)_readerWeak.Target;
        if (dataTableReader != null)
        {
            dataTableReader.DataTableCleared();
        }
        else
        {
            UnSubscribeEvents();
        }
    }
 
    private void SchemaChanged(object sender, CollectionChangeEventArgs e)
    {
        DataTableReader dataTableReader = (DataTableReader)_readerWeak.Target;
        if (dataTableReader != null)
        {
            dataTableReader.SchemaChanged();
        }
        else
        {
            UnSubscribeEvents();
        }
    }
 
    private void DataChanged(object sender, DataRowChangeEventArgs args)
    {
        DataTableReader dataTableReader = (DataTableReader)_readerWeak.Target;
        if (dataTableReader != null)
        {
            dataTableReader.DataChanged(args);
        }
        else
        {
            UnSubscribeEvents();
        }
    }
}