Hi andysujoto, Inside the Template Field Text Box, add: onblur="verify_text(this);" Add the script to check for something: (my example should check if textbox was left empty) Haven't tried this example, but I used similar before. I have a sample code for this, but there is a problem when I'm converting My c# functions return value to the var its throwing some error, If you have any idea on this fix it and use it. provides a convenient way to realize data validation before it is committed to the underlying data source.

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When you display data entry functionality to users, you frequently have to validate the data entered into your form.

The Data Bound Item will be updated only if the cell is validated.

However, the user may prefer to validate all the data cells in a row at once.

The Data Grid View class provides a convenient way to perform validation before data is committed to the data store.

You can validate data by handling the Cell Validating event, which is raised by the Data Grid View when the current cell changes.However, pressing the Esc key in this situation will revert the initial value of the cell and it will close the editor. The Row Validating event has a slightly different behavior.When the validation fails, the editor is closed, but the user cannot change the current row in the grid until a valid cell value is entered.Let's assume that the If the user enters empty string for a specific cell and tries to navigate to another row, the validation fails and the Error Text is displayed on the corresponding row.At this point the user is not allowed to cancel the performed changes, pressing the Esc key.I handle the validation in the Cell Validating event, and if the cell is invalid display an error message, then cancel the exit of edit mode.