<Window x:Class="WpfApp1.MainWindow"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:local="clr-namespace:WpfApp1"
     mc:Ignorable="d"
     Title="MainWindow" Height="450" Width="800">
     <Grid>
          <Grid.ColumnDefinitions>
               <ColumnDefinition Width="auto"/>
          </Grid.ColumnDefinitions>

          <!-- ComboBox with binding text-->
          <ComboBox Grid.Column="0"
               ItemsSource="{Binding MyData1}"
               Text="{Binding MyText1}"
               DisplayMemberPath="BookName"
               IsEditable="true"
               Height="25" Width="250" />
     </Grid>
</Window>

using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp1
{

     public class Book
     {
          public string BookName { get; set; }
          public int Price { get; set; }
     }

     /// <summary>
     /// Interaction logic for MainWindow.xaml
     /// </summary>
     public partial class MainWindow : Window
     {
          public MainWindow()
          {
               // fill data for ComboBox
               var list = new List<Book>();
               list.Add(new Book() { BookName = "aaaa", Price = 10 });
               list.Add(new Book() { BookName = "bbbb", Price = 20 });
               _myData1 = list;

               InitializeComponent();

               // for binding
               this.DataContext = this;
          }

          public string MyText1 { get; set; }

          private IEnumerable<Book> _myData1;

          public IEnumerable<Book> MyData1
          {
               get { return _myData1; }
               set { }
          }
     }
}