 <p>Got the answer:</p> <p>When trying to upload file using IE, its taking my filename as <code>C:\Users\user_name\Downloads\myfile.csv</code> instead of <code>myfile.csv</code></p> <p>so replaced <code>this.GetCmp&lt;FileUploadField&gt;("FileUpload").PostedFile.FileName</code> with <code>Path.GetFileName(this.GetCmp&lt;FileUploadField&gt;("FileUpload").PostedFile.FileName)</code> in <code>client.UploadFile(..)</code> above.</p>