Роман

Users
    .Where(u => u.Books
    .Any(b => b.Author == "Достоевский"))
    .Select(u => u.Name)

public class AuthorizeModel
{
	public string Login { get; set; }
	public string Password { get; set; }
}

Web API reads the response body at most once, so only one parameter of an action can come from the request body. If you need to get multiple values from the request body, define a complex type.

static void Main()
        {
            string[] m = new string[] { "один", "пять", "десять" };
            string s = "два три один";

            //1 Способ
            if (m.Any(x => s.IndexOf(x) >= 0))
            {
                //any code
            }

            //2 Способ
            if (m.Intersect(s.Split()).Any())
            {
                //any code
            }
        }

public static void Main()
{
}

public static void Main(string[] args)
{
}

public static int Main()
{
}

public static int Main(string[] args)
{
}

IEnumerable<T> traverse(Node current) {
    if (current != null)
    {
        foreach (var value in traverse(current.left))
            yield return value;

        yield return current.value;

        foreach (var value in traverse(current.right))
            yield return value;
    }
}

<Grid>
        <Grid.ColumnDefinitions>
             <ColumnDefinition Width="*" />
             <ColumnDefinition Width="10" />
             <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <DataGrid Grid.Column="0" x:Name="DG_1"  />
        <DataGrid Grid.Column="2" x:Name="DG_2"  />
    </Grid>