c# - Could not load file or assembly TechTalk.SpecFlow, Version=1.9.0.77 -

i trying out bdd in visual studio 2013. have started fresh new blank project. have written feature file , steps definition. added specflow using nugget packages. installed specflow version 2.1.0 when build solution looking specflow version 1.9.0.77

when searched specflow in nugget packages 1 listed. installed , believe latest version 2.1.0 why solution looking older version of 1.9.0.77 ? if resolution install 1.9.0.77 how install , how find version in nugget?

the full error trace is:

custom tool error: generation error: not load file or assembly 'techtalk.specflow, version=1.9.0.77, culture=neutral, publickeytoken=0778194805d6db41' or 1 of dependencies. system cannot find file specified. e:\rl fusion\projects\bdd\c# bdd\youtubetutorial2\specflowfirst\specflowfirst\specflowfirst\features\googlesearch.feature   2   2   specflowfirst 

thanks, riaz

the imports are:

using baseclass.contrib.specflow.selenium.nunit.bindings; using openqa.selenium; using system; using system.collections.generic; using system.configuration; using system.linq; using system.text; using system.threading.tasks; using techtalk.specflow; using techtalk.specflow.assist; 

baseclass.contrib.specflow.selenium.nunit work specflow 1.9.0. claims work versions after 1.9, not true, because changed plugin- interface in specflow. did wanted use it, because of ability test against multiple browser 1 scenario?

if so, have @ example https://github.com/techtalk/specflow.plus.examples/tree/master/seleniumwebtest uses specflow+runner test runnner.
if follow that, have same functionality , can use latest version of specflow.

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full disclosure: 1 of developers of specflow , specflow+.