Coding⏱️ 2 min read📅 2026-06-03

How to Fix: This Row already belongs to another table error when trying to add rows?

Error occurs when trying to add duplicate rows to a DataTable.

Quick Answer: Use the "AddNewRow" method instead of "Add" to create new rows in a DataTable.

The error 'This Row already belongs to another table' occurs when you're trying to add a row from one DataTable to another that shares the same primary key, but with different data types or constraints.

⚠️ Common Causes

  • Using the same primary key column in both DataTables.

🔧 Proven Troubleshooting Steps

Method 1: Column Mismatch

  1. Step 1: Check the data types of the primary key column in both DataTables.

Method 2: Duplicate Primary Key

  1. Step 1: Check if the primary key column has any duplicate values in either DataTable.

Method 3: Use a Different Key

  1. Step 1: If the primary key column is not unique, use a different column as the key for the second DataTable.

🎯 Final Words

To resolve this issue, ensure that the primary key columns in both DataTables have the same data type and no duplicate values. Alternatively, use a different column as the key for the second DataTable if necessary.

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