ES-975464 - Resolve the ReadMe file length issue in this sample repository

Author: SreemonPremkumarM

README.md

@@ -0,0 +1,143 @@
+# How to create a custom column from existing column in wpf and uwp datagrid
+
+This repositories contains the samples to create custom column from existing columnm in [WPF DataGrid](https://www.syncfusion.com/wpf-controls/datagrid) and [UWP DataGrid](https://www.syncfusion.com/uwp-ui-controls/datagrid).
+
+You can create your own column by overriding the [predefined column types](https://help.syncfusion.com/wpf/datagrid/column-types#_Overriding_existing_cell) in `SfDataGrid`. For example, the `GridDateTimeColumn` loads the DateTime value by default. If you want to display `DateTimeOffset` value, you can create a new column by overriding the `GridDateTimeColumn` class.
+
+In the below code snippet, converter created to format the `DateTimeOffSet` value to DateTime by defining `ValueBinding` (edit) and `DisplayBinding` (non-edit).
+
+``` c#
+public class DateTimeOffsetFormatConverter : IValueConverter
+{
+    private GridDateTimeOffsetColumn cachedColumn;
+
+    public DateTimeOffsetFormatConverter(GridDateTimeOffsetColumn column)
+    {
+        cachedColumn = column;
+    }
+
+    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+    {
+        value = ((DateTimeOffset)value).DateTime;
+        var column = cachedColumn as GridDateTimeColumn;
+        if (value == null || DBNull.Value == value)
+        {
+            if (column.AllowNullValue && column.MaxDateTime != System.DateTime.MaxValue && column.NullText == string.Empty)
+                return column.MaxDateTime;
+
+            if (column.AllowNullValue && column.NullValue != null)
+                return column.NullValue;
+            else if (column.AllowNullValue && column.NullText != string.Empty)
+                return column.NullText;
+
+            if (column.MaxDateTime != System.DateTime.MaxValue)
+                return column.MaxDateTime;
+        }
+
+        DateTime _columnValue;
+        _columnValue = (DateTime)value;
+
+        if (_columnValue < column.MinDateTime)
+            _columnValue = column.MinDateTime;
+
+        if (_columnValue > column.MaxDateTime)
+            _columnValue = column.MaxDateTime;
+
+        return DateTimeFormatString(_columnValue, column);
+    }
+
+    private string DateTimeFormatString(DateTime columnValue, GridDateTimeColumn column)
+    {
+        switch (column.Pattern)
+        {
+            case DateTimePattern.ShortDate:
+                return columnValue.ToString("d", column.DateTimeFormat);
+            case DateTimePattern.LongDate:
+                return columnValue.ToString("D", column.DateTimeFormat);
+            case DateTimePattern.LongTime:
+                return columnValue.ToString("T", column.DateTimeFormat);
+            case DateTimePattern.ShortTime:
+                return columnValue.ToString("t", column.DateTimeFormat);
+            case DateTimePattern.FullDateTime:
+                return columnValue.ToString("F", column.DateTimeFormat);
+            case DateTimePattern.RFC1123:
+                return columnValue.ToString("R", column.DateTimeFormat);
+            case DateTimePattern.SortableDateTime:
+                return columnValue.ToString("s", column.DateTimeFormat);
+            case DateTimePattern.UniversalSortableDateTime:
+                return columnValue.ToString("u", column.DateTimeFormat);
+            case DateTimePattern.YearMonth:
+                return columnValue.ToString("Y", column.DateTimeFormat);
+            case DateTimePattern.MonthDay:
+                return columnValue.ToString("M", column.DateTimeFormat);
+            case DateTimePattern.CustomPattern:
+                return columnValue.ToString(column.CustomPattern, column.DateTimeFormat);
+            default:
+                return columnValue.ToString("MMMM", column.DateTimeFormat);
+        }
+    }
+
+    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}
+
+public class DateTimeOffsetToDateTimeConverter : IValueConverter
+{
+    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+    {
+        if (value == null)
+            return null;
+        return ((DateTimeOffset)value).DateTime;
+    }
+
+    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+    {
+        if (value == null)
+            return null;
+        return value is DateTimeOffset ? value : new DateTimeOffset((DateTime)value);
+    }
+}
+```
+
+In the below code snippet, `GridDateTimeOffsetColumn` column created from `GridDateTimeColumn`.
+
+``` c#
+public class GridDateTimeOffsetColumn : GridDateTimeColumn
+{
+    protected override void SetDisplayBindingConverter()
+    {
+        if ((DisplayBinding as Binding).Converter == null)
+            (DisplayBinding as Binding).Converter = new DateTimeOffsetFormatConverter(this);
+
+        if ((ValueBinding as Binding).Converter == null)
+            (ValueBinding as Binding).Converter = new DateTimeOffsetToDateTimeConverter();
+    }
+}
+```
+
+In the below code snippet, created `GridDateTimeOffsetColumn` added to `SfDataGrid.Columns` collection and specify the Pattern as FullDateTime. Since the ShortDate is the default pattern of `GridDateTimeColumn`.
+
+### XAML
+
+``` xml
+<syncfusion:SfDataGrid  x:Name="dataGrid"                                                                       
+                        AutoGenerateColumns="False" 
+                        ItemsSource="{Binding Orders}">
+    <syncfusion:SfDataGrid.Columns>
+        <local:GridDateTimeOffsetColumn MappingName="OrderDate" Pattern="FullDateTime"        UseBindingValue="True"/>
+    </syncfusion:SfDataGrid.Columns>
+</syncfusion:SfDataGrid>
+```
+
+### C#
+
+``` c#
+this.datagrid1.Columns.Add(new GridDateTimeOffsetColumn()
+{
+    MappingName = "OrderDate",
+    Pattern = Syncfusion.Windows.Shared.DateTimePattern.FullDateTime,
+    UseBindingValue = true
+});
+```