Appium C# sendroid mode not working on Webview

HI,

I am using C# Appium with selendroid mode (Android version 4.2.2 Api lavel 17).
I have written below code but unable to click on the object, please help me

       private AndroidDriver<AppiumWebElement> driver;

        System.Diagnostics.Process process = new System.Diagnostics.Process();
        System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
        startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
        startInfo.FileName = "C:/Program Files/nodejs/node.exe";
        startInfo.Arguments = @"""C:/Users/xyz/AppData/Roaming/npm/node_modules/appium/build/lib/appium.js""--address 127.0.0.1 --port 4723 --automation-name Appium --log-no-color";
        process.StartInfo = startInfo;
        process.Start();

        capabilities.SetCapability(CapabilityType.BrowserName, "");
        capabilities.SetCapability(CapabilityType.Platform, "Android");
        capabilities.SetCapability("automationName", "Selendroid");
        capabilities.SetCapability(MobileCapabilityType.PlatformVersion, "4.2.2");
        capabilities.SetCapability("locationContextEnabled", true);
        capabilities.SetCapability("deviceName", "xyzzz");
        capabilities.SetCapability(MobileCapabilityType.App, "D:\\xyz.apk");
        capabilities.SetCapability(AndroidMobileCapabilityType.AppPackage, "xyz.pqr.com");
        capabilities.SetCapability(AndroidMobileCapabilityType.AppActivity, ".xyzActivity");

        driver = new AndroidDriver<AppiumWebElement>(new Uri("http://127.0.0.1:4723/wd/hub"), capabilities);


        var contexts2 = ((IContextAware)driver).Contexts;
        string webviewContext2 = null;
        for (int ii = 0; ii < contexts2.Count; ii++)
        {
            Console.WriteLine(contexts2[ii]);
            if (contexts2[ii].Contains("WEBVIEW"))
            {
                webviewContext2 = contexts2[ii];
                break;
            }
        }
        ((IContextAware)driver).Context = webviewContext2; // webviewContext2 I am getting WEBVIEW_0

       driver.FindElement(By.XPath("//*[@id='myusername']")).Click(); // it's failing here

Getting error ‘An element could not be located on the page using the given search parameters’
It’ll be great if you’ll provide me the solution for the same

Thanks in advance.

Thanks,
Smita