How to sort the grouped column based on custom group text

In the WPF DataGrid (SfDataGrid), when we applying the Custom grouping, the default sorting behavior applied for custom text. It sorts the view based on key values only when grouped the columns. However, this behavior can be customized using the SortComparer method to achieve sorting based on custom group property values.

public class CustomComparer : IComparer<object>, ISortDirection

{
    public int Compare(object x, object y)
    {
        DateTime nameX = new DateTime();
        DateTime nameY = new DateTime();

        //While data object passed to comparer
        if (x.GetType() == typeof(SalesByDate))
        {
            nameX = ((SalesByDate)x).Date;
            nameY = ((SalesByDate)y).Date;
        }

        //While sorting groups
        else if (x.GetType() == typeof(Group))
        {
            //Calculating the group key length
            nameX = ((((Group)x).Records[0] as RecordEntry).Data as SalesByDate).Date;
            nameY = ((((Group)y).Records[0] as RecordEntry).Data as SalesByDate).Date;
        } 

        //returns the comparison result based in SortDirection.
        if (nameX < nameY)
            return SortDirection == ListSortDirection.Ascending ? 1 : -1;
        else if (nameX > nameY)
            return SortDirection == ListSortDirection.Ascending ? -1 : 1;
        else
            return 0;
    }

    private ListSortDirection _SortDirection;

    /// <summary>
    /// Gets or sets the property that denotes the sort direction.
    /// </summary>
    /// <remarks>
    /// SortDirection gets updated only when sorting the groups. For other cases, SortDirection is always ascending.
    /// </remarks>
    public ListSortDirection SortDirection
    {
        get { return _SortDirection; }
        set { _SortDirection = value; }
    }
}

You can attach this in the Xaml code by using the below mentioned code snippet,

<window.resources>
    <local:groupdatatimeconverter x:key="customGroupDateTimeConverter">
    <local:customcomparer x:key="Comparer">
</local:customcomparer></local:groupdatatimeconverter></window.resources>


<syncfusion:sfdatagrid.sortcomparers>
    <linq:sortcomparer comparer="{StaticResource Comparer}" propertyname="Date">
</linq:sortcomparer></syncfusion:sfdatagrid.sortcomparers>

Take a moment to peruse the WPF DataGrid - Custom Sorting documentation, where you can find about the clipboard operations with code examples.