在PictureBox中打开图片文件

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void import_Click(object sender, EventArgs e)
    {
        OpenFileDialog openfile = new OpenFileDialog();

        openfile.Filter = "jpg类型图片(*.jpg)|*.jpg|BMP类型图片(*.bmp)|*.bmp";
        if (openfile.ShowDialog() == DialogResult.OK)
        {
            //第一步，打开图片文件，获得比特流，生成字节数组。
            byte[] picbinary = GetFileBytes(openfile.FileName);
            //第二步，将比特流存在内存工作流中
            MemoryStream mempicstream = new MemoryStream(picbinary);
            //加载内存流到图片控件
            this.pictureBox1.Image = Image.FromStream(mempicstream);
            mempicstream.Dispose();
            mempicstream.Close();
        }
    }

    public byte[] GetFileBytes(string Filename)
    {
        if (Filename == "")
            return null;
        try
        {
            FileStream fileStream = new FileStream(Filename, FileMode.Open,
              FileAccess.Read);
            BinaryReader binaryReader = new BinaryReader(fileStream);
            byte[] fileBytes = binaryReader.ReadBytes((int)fileStream.Length);
            binaryReader.Close();
            return fileBytes;
        }
        catch
        {
            return null;
        }
    }
}

显示完整图片：

pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;