如何使用链接按钮下载图片？ [英] How to download image using link button?
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问题描述
我正在尝试使用链接按钮下载图片。任何人都知道如何使用链接按钮下载图像。帮我找到一个正确的解决方案。谢谢。
代码：
protected void Page_Load（object sender ，EventArgs e）
{
if（！IsPostBack）
{
pdfDataSetTableAdapters.tbl_imgTableAdapter td;
td = new pdfDataSetTableAdapters.tbl_imgTableAdapter（）;
DataTable dt = new DataTable（）;
dt = td.GetId（）;
DropDownList1.DataSource = dt;
DropDownList1.DataTextField =Id;
DropDownList1.DataValueField =Id;
DropDownList1.DataBind（）;
DropDownList1.Items.Insert（0，new System.Web.UI.WebControls.ListItem（ - Select Id--，））;
}
}
protected void Button1_Click（object sender，EventArgs e）
{
pdfDataSetTableAdapters.tbl_imgTableAdapter td;
td = new pdfDataSetTableAdapters.tbl_imgTableAdapter（）;
DataTable dt = new DataTable（）;
dt = td.GetImg（int.Parse（DropDownList1.SelectedValue））;
foreach（dt.Rows中的DataRow行）
{
byte [] img2 =（byte []）row [img];
string base2 = Convert.ToBase64String（img2）;
Image1.ImageUrl =data：image / jpg; base64，+ base2;
}
}
protected void LinkButton1_Click（object sender，EventArgs e）
{
string sFile = Image1.ImageUrl;
if（string.IsNullOrEmpty（sFile））
{
return;
}
FileInfo fi = new FileInfo（Server.MapPath（sFile））; // error popup here
if（！fi.Exists）
{
return;
}
if（！string.IsNullOrEmpty（sFile））
{
//检查文件是否为图像
NameValueCollection imageExtensions = new NameValueCollection（）;
imageExtensions.Add（。jpg，image / jpeg）;
imageExtensions.Add（。gif，image / gif）;
imageExtensions.Add（。png，image / png）;
if（imageExtensions.AllKeys.Contains（fi.Extension））
{
Response.ContentType = imageExtensions.Get（fi.Extension）;
Response.AppendHeader（Content-Disposition，attachment; filename =+ fi.Name）;
Response.TransmitFile（fi.FullName）;
Response.End（）;
}
Response.Redirect（sFile）;
}
ASPX：
< asp：DropDownList ID =DropDownList1runat =serverAutoPostBack =True> < / ASP：DropDownList的>
< asp：Button ID =Button1runat =serverOnClick =Button1_ClickText =Show/>
< asp：LinkButton ID =LinkButton1runat =server>下载< / asp：LinkButton>
< asp：Image ID =Image1runat =server/>
SQL1：
code> SELECT Id FROM tbl_img
SQL2：
SELECT img FROM tbl_img WHERE（Id = @Id）
DB：
O / P屏幕：
以下是实际输出。首先我们要从下拉列表中选择id，然后点击show按钮，然后在页面上显示适当的图像。我想通过点击下载链接按钮下载该图像。帮我找一个解决方案。谢谢。
错误：
解决方案
将以下代码添加到链接按钮单击事件。
代码
string sFile = Image1.ImageUrl;
//确保提供文件链接
if（string.IsNullOrEmpty（sFile））
{
return;
}
//确保文件存在
FileInfo fi = new FileInfo（Server.MapPath（sFile））;
if（！fi.Exists）
{
return;
}
if（！string.IsNullOrEmpty（sFile））
{
//检查文件是否为图像
NameValueCollection imageExtensions = new NameValueCollection（）;
imageExtensions.Add（。jpg，image / jpeg）;
imageExtensions.Add（。gif，image / gif）;
imageExtensions.Add（。png，image / png）;
if（imageExtensions.AllKeys.Contains（fi.Extension））
{
Response.ContentType = imageExtensions.Get（fi.Extension）;
Response.AppendHeader（Content-Disposition，attachment; filename =+ fi.Name）;
Response.TransmitFile（fi.FullName）;
Response.End（）;
}
Response.Redirect（sFile）;
}
添加以下命名空间以及
使用System.IO;
使用System.Collections;
使用System.Collections.Specialized;
I am trying to download image using link button. Any one know how to download a image using link button. Help me to find a proper solution. Thank you.
Code:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
pdfDataSetTableAdapters.tbl_imgTableAdapter td;
td = new pdfDataSetTableAdapters.tbl_imgTableAdapter();
DataTable dt = new DataTable();
dt = td.GetId();
DropDownList1.DataSource = dt;
DropDownList1.DataTextField = "Id";
DropDownList1.DataValueField = "Id";
DropDownList1.DataBind();
DropDownList1.Items.Insert(0, new System.Web.UI.WebControls.ListItem("--Select Id--", ""));
}
}
protected void Button1_Click(object sender, EventArgs e)
{
pdfDataSetTableAdapters.tbl_imgTableAdapter td;
td = new pdfDataSetTableAdapters.tbl_imgTableAdapter();
DataTable dt = new DataTable();
dt = td.GetImg(int.Parse(DropDownList1.SelectedValue));
foreach (DataRow row in dt.Rows)
{
byte[] img2 = (byte[])row["img"];
string base2 = Convert.ToBase64String(img2);
Image1.ImageUrl = "data:image/jpg;base64," + base2;
}
}
protected void LinkButton1_Click(object sender, EventArgs e)
{
string sFile = Image1.ImageUrl;
if (string.IsNullOrEmpty(sFile))
{
return;
}
FileInfo fi = new FileInfo(Server.MapPath(sFile)); // error popup here
if (!fi.Exists)
{
return;
}
if (!string.IsNullOrEmpty(sFile))
{
// check if the file is an image
NameValueCollection imageExtensions = new NameValueCollection();
imageExtensions.Add(".jpg", "image/jpeg");
imageExtensions.Add(".gif", "image/gif");
imageExtensions.Add(".png", "image/png");
if (imageExtensions.AllKeys.Contains(fi.Extension))
{
Response.ContentType = imageExtensions.Get(fi.Extension);
Response.AppendHeader("Content-Disposition", "attachment; filename=" + fi.Name);
Response.TransmitFile(fi.FullName);
Response.End();
}
Response.Redirect(sFile);
}
ASPX:
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"> </asp:DropDownList>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Show" />
<asp:LinkButton ID="LinkButton1" runat="server">Download</asp:LinkButton>
<asp:Image ID="Image1" runat="server" />
SQL1:
SELECT Id FROM tbl_img
SQL2:
SELECT img FROM tbl_img WHERE (Id = @Id)
DB:
O/P Screen: Given below is the actual out put. first we have to select id from drop down list, after that click on show button then it display appropriate image on page. I want to download that image by clicking the download link button. Help me to find a solution. Thank you.
ERROR:
解决方案
Add the following code to your Link Button Click event.
Code
string sFile = Image1.ImageUrl;
// make sure file link is provided
if (string.IsNullOrEmpty(sFile))
{
return;
}
// make sure file exists
FileInfo fi = new FileInfo(Server.MapPath(sFile));
if (!fi.Exists)
{
return;
}
if (!string.IsNullOrEmpty(sFile))
{
// check if the file is an image
NameValueCollection imageExtensions = new NameValueCollection();
imageExtensions.Add(".jpg", "image/jpeg");
imageExtensions.Add(".gif", "image/gif");
imageExtensions.Add(".png", "image/png");
if (imageExtensions.AllKeys.Contains(fi.Extension))
{
Response.ContentType = imageExtensions.Get(fi.Extension);
Response.AppendHeader("Content-Disposition", "attachment; filename=" + fi.Name);
Response.TransmitFile(fi.FullName);
Response.End();
}
Response.Redirect(sFile);
}
Add the following namespaces as well.
using System.IO;
using System.Collections;
using System.Collections.Specialized;
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