The difference between my and @Junaith output from ILSpy lead me to tought that I'm looking at wrong file -C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\Profile\Client\System.Windows.Forms.DataVisualization.dll
. This path I obtained from comment at top of metadata of System.Windows.Forms.DataVisualization.Charting.DataFormula
viewed by using "Go to Definition" VS function on member method DataManipulator.FinancialFormula of Chart.
So I ran my program and with Process Explorer I looked on loaded .NET Assemblies in properties of my program process. For my surprise the dll mentioned before wasn't even there, instead I found there C:\Windows\assembly\NativeImages_v4.0.30319_32\System.Wind0de890be#\a4711c664a774896b35428b1a3bf9470\System.Windows.Forms.DataVisualization.ni.dll
.
I loaded that dll into ILSpy and methods have full implementation including their bodies.