I have a table in a SQL DB with a primary key where null is NOT allowed = no checkmark in the table definition.

If you want to show the error message, you can handle the CellValidating event.

Something like :

private void refer01DataGridView_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)

{

if (e.ColumnIndex == 0)

{

if (e.FormattedValue.ToString().Trim() == "")

{

MessageBox.Show("Not allow null");

e.Cancel = true;

}

}

}

---

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Oh ... my God !

The bindingnavigator is the cause ... !

It's so easy to Drag&Drop a datasource to a form and get your data presented in a datagridview and it SEEMS like it's working ... but it's not !

One of my columns is the primary key in the DB and null values is NOT allowed in the DB in this field.

But you can add a new row in the datagridview, move away from the primary key column, enter some values in the other columns and now it comes .... click on the "move to previous" key and wupti the row is saved with a primary key as a string of length 0 !

How can this Drag&Drop method be made secure concerning data validation ?

Hi PSAKSor,

Could you please upload your project or a demo project and the database? That will help us make the issue more clearly.

Base on my understanding, there may be something wrong with the datatable(or dataset) in the project. Are you sure the null value can be saved which the corresponding column is not allowed null value? If so, I think you need to refresh the dataset in the databse and see if the corresponding column has a right setting. If not, I think there may be something wrong in the code.

Look forward to your reply.

Best regards,

Ling Wang

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As I did write in my post "now it comes .... click on the "move to previous" key and wupti the row is saved with a primary key as a string of length 0 !"

It's a string of length 0 witch I think is the problem - it should taken care of.

If the primary key is identity, when saving the null value, the SQL Server will fill the blank with the corresponding value automatically.

Do you mean you problem has been solved? If not, please feel free to ask.

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I don't think it's solved because I wants the user to see a message like "You should enter a primary key !" and then set focus back in the right column in the datagridview or textbox.

Where should I test for the "string of length 0" ?(with I believe is NOT a null string - right ?)

If you want to show the error message, you can handle the CellValidating event.

Something like :

private void refer01DataGridView_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)

{

if (e.ColumnIndex == 0)

{

if (e.FormattedValue.ToString().Trim() == "")

{

MessageBox.Show("Not allow null");

e.Cancel = true;

}

}

}

---

Please remember to click “Mark as Answer�on the post that helps you, and to click “Unmark as Answer�if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.