将图片以二进制的方式保存在数据库中，并显示图片

http://www.aspnettutorials.com/tutorials/database/store-img-bins-asp4-cs/

http://stackoverflow.com/questions/18998763/how-to-retrieve-binary-image-from-database-using-c-sharp-in-asp-net

 在GridView里面显示图片，当单击这个图片的时候，放大显示这个图片

http://www.aspsnippets.com/Articles/Display-GridView-images-with-LightBox-effect-whenever-user-clicks-on-images-in-ASPNet.aspx

1. 创建一个数据表

CREATE TABLE [dbo].[SaveImageByBinary]
(
   [Id] INT NOT NULL PRIMARY KEY IDENTITY, 
    [Image] VARBINARY(MAX) NULL,    
    [ImageName] NVARCHAR(MAX) NULL
)

 2. HTML 页面

 <div>
        <asp:FileUpload ID="FileUpload1" runat="server" />
        <asp:Button ID="Button1" runat="server" Text="SaveImage" OnClick="Button1_Click"/><hr />    //保存上传的文件
        <asp:Image ID="Image1" runat="server" /><br /> //显示图片
        <asp:Button ID="Button2" runat="server" Text="DisplayImage" OnClick="Button2_Click"/><br />  //第二种方式显示图片
        <img id="img" runat="server" alt=""/><br />
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label> 
    </div>

3.将图片以二进制的方式保存到数据库

 protected void Button1_Click(object sender, EventArgs e)
        {
            
            if (FileUpload1.PostedFile != null && !string.IsNullOrEmpty(FileUpload1.PostedFile.FileName))
            {
               
                byte[] Image = new byte[FileUpload1.PostedFile.ContentLength];
              
                HttpPostedFile img = FileUpload1.PostedFile;
                img.InputStream.Read(Image, 0, (int)FileUpload1.PostedFile.ContentLength);

                SqlConnection conn = new SqlConnection(WebConfigurationManager.ConnectionStrings["DemosDatabaseConnectionString"].ConnectionString);
                SqlCommand cmd = new SqlCommand("INSERT INTO SaveImageByBinary([Image],ImageName) VALUES (@ImgBin,@ImageName)", conn);
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.Add("@ImgBin", SqlDbType.Image, Image.Length).Value = Image;
                cmd.Parameters.Add("@ImageName", SqlDbType.NVarChar).Value = FileUpload1.FileName;
                using (conn)
                {
                    //open the connection
                    conn.Open();
                    //send the sql query to store the data
                    cmd.ExecuteNonQuery();
                    Response.Write("Succeed");
                }
            }
            else
            {
                byte[] Image = new byte[FileUpload1.PostedFile.ContentLength];

                HttpPostedFile img = FileUpload1.PostedFile;
                img.InputStream.Read(Image, 0, (int)FileUpload1.PostedFile.ContentLength);

                SqlConnection conn = new SqlConnection(WebConfigurationManager.ConnectionStrings["DemosDatabaseConnectionString"].ConnectionString);
                SqlCommand cmd = new SqlCommand("INSERT INTO SaveImageByBinary([Image],ImageName) VALUES (@ImgBin,@ImageName)", conn);
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.Add("@ImgBin", SqlDbType.Image, Image.Length).Value = Image;
                cmd.Parameters.Add("@ImageName", SqlDbType.NVarChar).Value = FileUpload1.FileName;
                using (conn)
                {
                    //open the connection
                    conn.Open();
                    //send the sql query to store the data
                    cmd.ExecuteNonQuery();
                    Response.Write("Succeed");
                }
            }
        }

4. 从数据库中取出数据并以二进制的方式显示图片（需要用一个事件调用这个方法）

   public void DisplayImage_BinaryStyle()
        {
            //connect to the db
            SqlConnection conn = new SqlConnection(WebConfigurationManager.ConnectionStrings["DemosDatabaseConnectionString"].ConnectionString);
            //sql command to select the image with id of 1
            SqlCommand cmd = new SqlCommand("SELECT * FROM SaveImageByBinary WHERE Id=@ImgId", conn);
            cmd.CommandType = CommandType.Text;
            //select the image with ImgId of 1
            cmd.Parameters.AddWithValue("@ImgId", 1);
            using (conn)
            {
                //open the connection
                conn.Open();
                //send the sql query to select the image and store the results in a sqldatareader
                SqlDataReader rdr = cmd.ExecuteReader();
                //read the data
                if (rdr.Read())
                {
                    Byte[] imgData = (byte[])rdr["Image"];
                    Response.OutputStream.Write(imgData, 0, imgData.Length);
                }
            }
        }

5. 调用事件，显示图片

  protected void Button2_Click(object sender, EventArgs e)
        {
            Image1.ImageUrl = "SaveImageByBinary.aspx";
            DisplayImage_BinaryStyle();
        }

--------------------------------------------------------------

第二种方式读取数据库中的二进制数据，并进行显示图片

   protected void Button2_Click(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection(WebConfigurationManager.ConnectionStrings["DemosDatabaseConnectionString"].ConnectionString);
            SqlDataAdapter sda = new SqlDataAdapter("select * from SaveImageByBinary",conn);
            DataTable dt = new DataTable();
            sda.Fill(dt);

            foreach (DataRow row in dt.Rows)
            {
                
                //Get the byte array from image file
                byte[] imgBytes = (byte[])row["Image"];
                string ImgName = row[2].ToString();

                //If you want convert to a bitmap file
                TypeConverter tc = TypeDescriptor.GetConverter(typeof(Bitmap));
                Bitmap MyBitmap = (Bitmap)tc.ConvertFrom(imgBytes);


                string imgString = Convert.ToBase64String(imgBytes);
                //Set the source with data:image/bmp
                img.Src = String.Format("data:image/Bmp;base64,{0}"", imgString);
                Label1.Text = ImgName;
            }
        }