How to know source function and source data when debug on visual studio 2015

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C#6.0

Problem
How to know that subfunction2 come from subfunction1 or with another meaning

it source of subfunction2 exist on subfunction1 ?

I work on csharp language on visual studio 2015 windows form

I implement and develop big module and have more functions nested on another functions

i need when make breakpoint to function to know this function come from any place or

with another way what calling to this function done before it called and data on function

come from any place I ask this question because i work on project have more functions

nested on each others and in different places and different files

What I have tried:

Public Datatable MainFunction(string data)
{
datatable dt1=SubFunction1(string data);
}
Public Datatable SubFunction1(string data)
{
datatable dt2=SubFunction2(string data);
}
Public Datatable SubFunction2(string data)
{

}

when debug and found exception on SubFunction2

How to know that subfunction2 come from subfunction1 or with another meaning 

 source of subfunction2 exist on subfunction1