如何添加2个字段的内容以获取XAML代码中的摘要？

I would like to know how to get the column summary in XAML code. I'm able to get the row summaries using the code mentioned in attachment or image. But I do not know how to add contents from "a1" ,"b1" and "c1" to get the "Summary" in XAML code only without using code-behind . I'm using Infragistics xamDataGridI would like to know how to get the column summ