getting an error while creating a console app using C# as - Cannot create an instance of the abstract type or interface SmartsheetClient

Question

I created a console app to access the sheet data . first I added the smartsheet-csharp-sdk package using nuget version 3.1.1.Then I started writing the code . after writing the line- SmartsheetClient smartsheet = new SmartsheetClient(accessToken);

it is giving the error - Cannot create an instance of the abstract type or interface SmartsheetClient

I am trying to get the data from the smartsheet using accesstoken and sheetId, but it is giving the error