(Contribution) New API member Must Exist Error on Build

[sps014]

Is there any procedure that one must keep in mind while adding a new API?

I have added a Member in IList Interface and implemented this in relevant classes.
Now when I build the.net, I received the following error.

MembersMustExist : Member 'public void System.Collections.Generic.List<T>.RemoveAt(System.Index)' 
does not exist in the reference but it does exist in the implementation.

I added the above error in runtime\src\libraries\System.Collections\src\MatchingRefApiCompatBaseline.txt as was suggested in the previous full error.
Now I am receiving the following error

microsoft.dotnet.apicompat\6.0.0-beta.21425.3\build\Microsoft.DotNet.ApiCompat.targets(82,5): error :
 InterfacesShouldHaveSameMembers : Interface member 'public void System.Collections.IList.RemoveAt(System.Index)' is present 
in the implementation but not in the contract. 
[C:\Users\shive\Desktop\Projects\runtime\src\libraries\System.Runtime\src\System.Runtime.csproj]
C:\Users\shive\.nuget\packages\microsoft.dotnet.apicompat\6.0.0-beta.21425.3\build\Microsoft.DotNet.ApiCompat.targets(96,5): 
error : ApiCompat failed for 'C:\Users\shive\Desktop\Projects\runtime\artifacts\bin\System.Runtime\net6.0-Debug\System.Runtime.dll'
 [C:\Users\shive\Desktop\Projects\runtime\src\libraries\System.Runtime\src\System.Runtime.csproj]

[gfoidl]

See Updating Ref source.

But keep in mind, that new APIs need to be approved first. Please check API Review Process for more infos on that side.

[sps014]

Thanks