Add user to Power BI Group

I am trying to programmatically give permission to a user for a particular dataset in power bi. Normally what we do in Power BI site is to navigate to the Workspace, select the dateset, from the popup menu select "security", from there add user in the "row level security". My clients requirement is to do the same programmatically from clients end using a web site.

So far I  have solved the initial error which is : "AADSTS70002: The request body must contain the following parameter: 'client_secret or client_assertion". This was because I had created a Power BI Server sideWeb app instead of a native app. Now I use a native app and I am getting a token.

I am getting the dataset info using the below code. But I need to access the Row level users list. Is there anyway which I can update the row level users list?

 //Get all Datasets of the group                   
var set = client.Datasets.GetDatasetsInGroup(GroupId);

//Get the target dataset
var targetSet = client.Datasets.GetDatasetsInGroup(GroupId).Value.Select(d=>d.Name=="ABC Reporting");