ASP.NET WebForms: Uploading, Validating And Displaying of Image

Introduction

Many years ago, I wrote a series of blog posts that demonstrates the following:

• Uploading and Storing Images to Database in ASP.NET
• Displaying Image to Image Control based on User Selection in ASP.NET
• FAQ: Displaying Image from Database to GridView Control
• Uploading and Storing Image Path to Database and Image to Folder - Part 1
• Uploading and Storing Image Path to Database and Image to Folder - Part 2 (Displaying of Images)
• Validate Image extensions upon Upload

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.

Using the Code

The folder structure should look something like this below:

• 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:

protected void Button1_Click(object sender, EventArgs e) {  
             StartUpLoad();  
}  
     
private void StartUpLoad() {  
        string imgName = string.Empty;  
        int imgSize = 0;
        string imgPath = string.Empty;       
       
       //validates the posted file before saving  
        if (FileUpload1.PostedFile != null && FileUpload1.PostedFile.FileName != "") {  
              //get the file name of the posted image           
              imgName = FileUpload1.PostedFile.FileName; 
               //sets the image path           
              imgPath = "ImageStorage/" + imgName; 
              //get the size in bytes that  
              imgSize = FileUpload1.PostedFile.ContentLength;  
              // 10240 KB means 10MB, You can change the value based on your requirement  
                if (imgSize > 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);  
                }    
          }  
}  

The code above is pretty much self-explanatory, but it think it should be worth explaining what the code does. The StartUpload() method contains the logic for saving the uploaded image to the specified folder location, which is under Project Root/ImageStorage. It also handles couple of basic validations for checking the PostedFile and ContentLength. If the validation fails, then it will trigger an alert popup to let the end user know that something is wrong, otherwise it will save the file to the system and then set the uploaded path as the ImageUrl of the Image control.

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