Developing Custom SSIS Data Flow Component: helpful links

Great resource to start with. A sample source code is also available for download.
http://geekswithblogs.net/Compudicted/archive/2012/03/01/creating-a-custom-ssis-data-flow-component---an-example.aspx

How to work with Connections
https://docs.microsoft.com/en-us/sql/integration-services/extending-packages-custom-objects-data-flow-types/developing-a-custom-source-component

Debugging Custom component
https://docs.microsoft.com/en-us/sql/integration-services/extending-packages-custom-objects/building-deploying-and-debugging-custom-objects

1. Component Project in DEBUG mode
2. register .dll in GAC and copy it in the DTS\PipelineComponents
3. in SSIS project: breakpoint on Pre-Execute of the Data Flow Task. Wait till we hit breakpoint
4. in Component project - Debug - > Attach to process. Select DtsDebugHost.exe (Managed, x64)
5. in Component project - put a breakpoint in code in Validate or PreExecute or ProcessInput
6. in SSIS project: click Continue
7. you should hit the breakpoint in the Component project

Automate with Post-build event: registering .dll in GAC and copying it in the DTS\PipelineComponents
http://toddmcdermid.blogspot.ca/2009/01/custom-component-developing-post-build.html

this worked:
copy "$(TargetDir)$(TargetName).DLL" "C:\Program Files (x86)\Microsoft SQL Server\110\DTS\PipelineComponents\"
gacutil.exe -i "$(TargetDir)$(TargetName).DLL"

Supporting different SQL Server platforms:

Support multi-targeting in your custom components

Getting your SSIS custom extensions to be supported by the multi-version support of SSDT 2015 for SQL Server 2016

Using PerformUpgrade

https://www.red-gate.com/simple-talk/sql/ssis/developing-a-custom-ssis-source-component/

https://blogs.perficient.com/microsoft/2016/04/developing-custom-ssis-component-9-lessons-learned/