ASP.NET WebForms: Uploading, Validating And Displaying Images

I wrote a series of blog posts awhile back before that demonstrates the following:

In this post I'm going to demonstrate how to upload an image to a specified folder within the root of the web application and display the image right away in the Image control after uploading. To get started let's go ahead and fire up Visual Studio and create a new Website/Web Application project. After that, create a folder under the root application for storing the uploaded images. The folder structure should look something like this below:

Solution

Application Name
AppCode
AppData
ImageStorage - //we will save the images in this folder
Default.aspx
web.config

For the simplicity of this demo, I just set up the HTML form like below:

<asp:FileUpload ID="FileUpload1" runat="server" />
<asp:Button ID="Button1" runat="server" Text="Upload" onclick="Button1_Click"/>
<br />
<asp:Image ID="Image1" runat="server" />

And here's the code for uploading the image to a folder.

protected void Button1_Click(object sender, EventArgs e) {
StartUpLoad();
}
private void StartUpLoad() {
//get the file name of the posted image
string imgName = FileUpload1.FileName;
//sets the image path
string imgPath = "ImageStorage/" + imgName;
//get the size in bytes that
int imgSize = FileUpload1.PostedFile.ContentLength;
//validates the posted file before saving
if (FileUpload1.PostedFile != null && FileUpload1.PostedFile.FileName != "") {
// 10240 KB means 10MB, You can change the value based on your requirement
if (FileUpload1.PostedFile.ContentLength > 10240) {
Page.ClientScript.RegisterClientScriptBlock(typeof(Page), "Alert", "alert('File is too big.')", true);
} else {
//then save it to the Folder
FileUpload1.SaveAs(Server.MapPath(imgPath));
Image1.ImageUrl = "~/" + imgPath;
Page.ClientScript.RegisterClientScriptBlock(typeof(Page), "Alert", "alert('Image saved!')", true);
}
}
}

That simple! Now you should be able to see the image in the page after uploading.