Expression for Adding Computed column in DataTable with a percentage sign

I've a DataTable with a column VatRate retrieved from database column of fl开发者_开发知识库oat DataType. Now I want to add a computed DataColumn in my DataTable with VatRate formated to two decimal places and a % sign followed by a space.

So if value in VatRate column is 12.5 then the value in ComputedColumn should be 12.50 %.

NOTE:

I want it on DisplayMember of Combobox

It would probably be easier to just bind that column to a e.g. DataGrid, and then define on the grid that this particular column should display with a fixed format, e.g. ##0.00 %.

In general: don't try to "force" your data to look like it should - try to define display properties on the UI for that!

The data is just the data - don't harass it with display options - those belong into the UI and not into your data.

Update:

In ASP.NET, the DropDownList e.g. has a property called DataTextFormatString which allows you to define a separate display format for your data.

The Winforms ComboBox class also has a property called FormatString that allows you to define how the data should look like.

Update #2: you're using Winforms - so set your FormatString on the combobox to:

this.comboBox1.FormatString = "#0.00 %";

and then fill in values like 0.0875, 0.125 and so forth - they'll be displayed as 8.75 % and 12.50 % respectively.

If formatting would not be an issue, you could have used an expression like this:

myDataColumn.Expression="Convert(VatRate, 'System.String') + '%'"

But why you need additional columns? Can't you simply assing a format string to the binding used to show the data in your From/Window/Page, or use a ToString(...) when writing in some stream?