二进制流上传图片，预览，读取显示

上传图片并生成缩略图预览效果

<div>
  <asp:FileUpload ID="FileUpload1" runat="server" CssClass="btn" Width="320px" onchange="getValue()" />&nbsp;<asp:Button ID="btnAdd" runat="server" Text="Submit" ValidationGroup="AddPlat" CssClass="btn" Width="80px" OnClick="btnAdd_Click" />
  <div id="t2" runat="server" style=" 150px; height: 120px; visibility: hidden; display: none; border: solid 1px #CCC;">
      <img alt="" id="t1" runat="server" src="" style=" 150px; height: 120px; border: solid 1px #CCC; display: none;" />
  </div>
  <asp:Image ID="imageSony" runat="server" BorderStyle="Solid" Width="150px" Height="120px" ImageUrl="" />
</div>

getvalue() Function的定义在一下Javascript中：

    <script type="text/javascript">
function getValue(){ 

    var isIE = (document.all) ? true : false;
    var isIE7 = isIE && (navigator.userAgent.indexOf('MSIE 7.0') != -1);
    var isIE8 = isIE && (navigator.userAgent.indexOf('MSIE 8.0') != -1);
    var isMozilla = /mozilla/.test( navigator.userAgent ) && !/(compatible|webkit)/.test( navigator.userAgent )
    var isOpera = /Opera/.test( navigator.userAgent )

    var t1=document.getElementById("t1")
    var t2=document.getElementById("t2")
    var imgsony=document.getElementById("imageSony")
    var t=document.getElementById("FileUpload1");
    var value=t.value
    
    t1.style.display="block";
    t2.style.display="block";
    imgsony.style.display="none";
    
    if(isIE7 || isIE8){
        t.select();
        var value=document.selection.createRange().text;
        document.selection.empty();
    }else if(isMozilla){
        value = t.files[0].getAsDataURL();
    }
    
    //alert(value)
    
    
    if(isIE7 || isIE8){
        t1.style.visibility="hidden"
        //t1.style.display="none";
        t2.style.visibility=""
        
        t1.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='image')"
        t1.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='scale')"
    
        t2.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='image')"
        t2.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='scale')"
    
        t1.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src=value;
        
        t2.style.width=t1.offsetWidth
        t2.style.height=t1.offsetHeight
    
        t2.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src=value;
    }else{
        t1.src=value
    }
}

    </script>

二进制流方式存入数据库

string fullFileName = FileUpload1.PostedFile.FileName;
//string fileName = fullFileName.Substring(fullFileName.LastIndexOf("\\") + 1);//图片名称
string type = fullFileName.Substring(fullFileName.LastIndexOf(".") + 1).ToLower();
if (type == "jpg" || type == "gif" || type == "bmp" || type == "png" || type == "jpeg")
{
      HttpPostedFile upFile = FileUpload1.PostedFile;//HttpPostedFile对象,用来读取上传图片的属性
     int fileLength = upFile.ContentLength;//记录文件的长度
     byte[] fileBytePicture = new byte[fileLength];//用图片的长度来初始化一个字节数组存储临时的图片文件
     Stream fileStream = upFile.InputStream;//建立文件流对象
     fileStream.Read(fileBytePicture, 0, fileLength);
      //Insert into db, picture字段，image类型
      //在此要注意，SQL语句中插入DB不能像varchar()类型，用单引号引起来，这样的话会报错，要使用参数自行插入，eg：
      //cmd.CommandText = @"INSERT INTO Category(Category,Picture)VALUES(@Category,@Picture)";
     //cmd.Parameters.AddWithValue("@Category", category);//string category
     //cmd.Parameters.AddWithValue("@Picture", picture);// byte[] picture
}

其中，Stream fileStream = upFile.InputStream;//建立文件流对象
        fileStream.Read(fileBytePicture, 0, fileLength);
建立文件流对象，生成二进制流必须存在，不能去掉，否则能够生成二进制流保存到数据库中。 

从数据库读取图片

BindItem();

 imageSony.ImageUrl = "ReadImage.aspx?itemid=" + itemID;

ReadImage.aspx.cs

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                string imageid = "1";
                if (Request.QueryString["itemid"] != null)
                {
                    imageid = Request.QueryString["itemid"].ToString();
                }
                int imgID = Int32.Parse(imageid);
                ShowImage(imgID);
            }
        }

        private void ShowImage(int itemID)
        {
            DataTable dt = new DataTable();
            dt = srb.GetSonyItem(itemID);//获得数据源
            byte[] b_image = (byte[])dt.Rows[0]["Picture"];//得到数据库二进制字段内容
            if (b_image.Length > 0)
            {
                Byte[] byteImg = (byte[])dt.Rows[0]["Picture"];
                Response.BinaryWrite(byteImg);//写入二进制流
                Response.End();
            }
        }