---
title: "Error: Unhandled exception has occurred in your application..."
canonical: "https://servicedesk.maxgeo.com/space/LC/1263632527/Error%3A%20Unhandled%20exception%20has%20occurred%20in%20your%20application..."
format: markdown
---
**Problem:**
You received the above error when Validating or Validating and Importing, and the second paragraph read:
1. A column named "X" alredy belongs to the Data Table - refer **Cause 1**.
**Troubleshooting:**
**Cause:**
1. Each column name is required to be unique, to ensure that the correct data is imported into the correct field. In this case, you have a column name (in place of "X" in the Problem 1 description) that appears more than once. Refer **Solution 1**.
**Solution:**
1. Rename one of more of these columns, such that each one is unique. While you're there, check the rest of your columns, or you might find this error repeating itself.