How to get key character using Virtual Key without using Native code?

I have need to get key character value from Virtual Key while type in TextBox. Currently we are using below code but it is not working in Release Mode

Platform : UWP

/// <summary>
/// Represents the KeyCode for keydown.
/// </summary>
internal class KeyCode
{
    /// <summary>
    /// Helps to get the UniCode based on input keys.
    /// </summary>
    /// <param name="key">input key.</param>
    /// <returns>Unicode.</returns>
    internal static string KeyCodeToUnicode(VirtualKey key)
    {
        byte[] keyboardState = new byte[255];
        bool keyboardStateStatus = GetKeyboardState(keyboardState);



        if (!keyboardStateStatus)
        {
            return string.Empty;
        }



        uint virtualKeyCode = (uint)key;
        uint scanCode = MapVirtualKey(virtualKeyCode, 0);
        IntPtr inputLocaleIdentifier = GetKeyboardLayout(0);



        StringBuilder result = new StringBuilder();
        int unicode = ToUnicodeEx(virtualKeyCode, scanCode, keyboardState, result, (int)5, 0, inputLocaleIdentifier);



        return result.ToString();
    }

    [DllImport("user32.dll", ExactSpelling = true)]
    private static extern bool GetKeyboardState(byte[] lpKeyState);



    [DllImport("user32.dll", ExactSpelling = true)]
    private static extern uint MapVirtualKey(uint uCode, uint uMapType);



    [DllImport("user32.dll", ExactSpelling = true)]
    private static extern IntPtr GetKeyboardLayout(uint idThread);



    [DllImport("user32.dll", ExactSpelling = true)]
    private static extern int ToUnicodeEx(uint wVirtKey, uint wScanCode, byte[] lpKeyState, [Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pwszBuff, int cchBuff, uint wFlags, IntPtr dwhkl);

}

Requirement: How to get key character while type in TextBox which needs work in both Release and Debug Mode.