<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" xmlns:WPFMediaKit="clr-namespace:WPFMediaKit.DirectShow.Controls;assembly=WPFMediaKit"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>


        <StackPanel>
            <ComboBox Name="cbCameras" SelectionChanged="cbCameras_SelectionChanged"/>
            <!--选摄像头-->
            <WPFMediaKit:VideoCaptureElement Height="200" x:Name="captureElement"/>
            <!--预览画面-->
            <Button Height="50" x:Name="btnCapture" Content="拍照" Click="btnCapture_Click"/>
            <!--拍照按钮-->
            <Image x:Name="img" />
        </StackPanel>
    </Grid>
</Window>

　　

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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;
using System.Runtime.InteropServices;
using WPFMediaKit.DirectShow.Controls;
using System.IO;

namespace WpfApp1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
            Loaded += MainWindow_Loaded;

        }
       
        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            cbCameras.ItemsSource = MultimediaUtil.VideoInputNames;
            if (MultimediaUtil.VideoInputNames.Length > 0)
            {
                cbCameras.SelectedIndex = 0;
            }
            else
            {
                MessageBox.Show("no video cap device");
            }
        }
        private void cbCameras_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            captureElement.VideoCaptureSource = (string)cbCameras.SelectedItem;
        }

        /// <summary>
        /// 拍照
        /// </summary>

        private void btnCapture_Click(object sender, RoutedEventArgs e)
        {
            //captureElement. 怎么抓取高清的原始图像           
            RenderTargetBitmap bmp = new RenderTargetBitmap(
                (int)captureElement.ActualWidth,
                (int)captureElement.ActualHeight,
                96, 96, PixelFormats.Default);

            //为避免抓不全的情况，需要在Render之前调用Measure、Arrange
            //为避免VideoCaptureElement显示不全，需要把
            //VideoCaptureElement的Stretch="Fill"
            captureElement.Measure(captureElement.RenderSize);
            captureElement.Arrange(new Rect(captureElement.RenderSize));
            bmp.Render(captureElement);
            //这里需要创建一个流以便存储摄像头拍摄到的图片。
            //当然，可以使文件流，也可以使内存流。
            BitmapEncoder encoder = new JpegBitmapEncoder();
            encoder.Frames.Add(BitmapFrame.Create(bmp));
             MemoryStream ms = new System.IO.MemoryStream();
            encoder.Save(ms);
            ms.Position = 0;
            BitmapImage b = new BitmapImage();
            b.BeginInit();
            b.StreamSource = ms;
            b.EndInit();
            img.Source = b;
            ms.Position = 0;
            FileStream f = File.Open("c:\\1.jpg", FileMode.OpenOrCreate);
            f.Write(ms.ToArray(), 0, (int)ms.Length);
            f.Close();

         

        }

    }

}