Object reference not set to an instance of the Object

The updated code snippet includes a null check for the ThumbImage property before assigning it to the ImageUrl of the img control. While this approach helps handle the case when ThumbImage is null, there are a few potential disadvantages to consider- 
1.  If ThumbImage is expected to have a non-null value, a null check and fallback to a default image might mask potential errors or issues in the data retrieval or assignment process. 
2. By using a default image for null ThumbImage values, all missing or null images will be represented by the same default image. 
3. Null values for ThumbImage could indicate missing or incomplete data. By using a default image as a fallback, it might not be immediately apparent to users or developers that an image is missing or that the data is incomplete.

Hi Ramco,

Have you checked what values you are getting in below line,

var img = e.Item.FindControl("imgThumb") as System.Web.UI.WebControls.Image;

if above one you are not getting cotrol from UI then it will create object reference error because you are trying to assing value to it. Try below one,

var img = e.Item.FindControl("imgThumb") as System.Web.UI.WebControls.Image;
                    BALBooks bALBooks = new BALBooks();
                    BookDetail objBook = bALBooks.GetBookList(Convert.ToInt32(hdfBookId.Value));
                    if (objBook != null)
                    {
                        if(objBook.ThumbImage != null && img != null)
                            img.ImageUrl = objBook.ThumbImage;
                    }

If the image control with ID "imgThumb" exists in the markup and you are still encountering the "Object reference not set to an instance of an object" error, there might be another issue causing the problem.

Here are a few additional troubleshooting steps you can follow:

1. Double-check that the image control is not nested inside any other container controls like panels, grids, or placeholders. If it is, make sure you are referencing it correctly in the FindControl method.

2. Ensure that the FindControl method is being called at the appropriate stage of the page lifecycle. It's best to call it after the control has been initialized and loaded. For example, you can try calling it in the Page_Load event handler or a similar event.

3. Verify that the control is of the correct type. In this case, the image control should be of type System.Web.UI.WebControls.Image. If the control is of a different type, you might encounter an error when trying to cast it to the Image type. Ensure that the control's type matches the expected type.

If you have confirmed that the image control exists, it might be helpful to provide more information about the context in which this code is being executed. Are you using any specific web framework or CMS? Are there any additional relevant code snippets or error messages? With more information, I can provide more targeted assistance