C# :: Update Then Delete Record In Datagridview

In my project i need to update the attn_dateTimeOut in database.After i updated it will automatic delete the specific row record that had been updated. I had two question:

1) in my database there are a few table is assign not null."attn_dateTimeOut" is a table that haven insert any record. When i update it using below code,it work and can update but it comes out error.Error show "record cannot be null".

2) I want t make it when i updated the "attn_dateTimeOut",it will auto delete the row of updated record.I do usign back code "DeleteRecord" but it nothing change!How should i do?

Here my code:

private void txt_proximity_KeyPress(object sender, KeyPressEventArgs e) {
if (e.KeyChar == (char)13) {
TMPB_attn row_TMPN_attn = BusinessLogicLayer.TMS_GET_PROXIMITY_VALID_TO_USE(txt_proximity.Text);
if (!String.IsNullOrEmpty(txt_proximity.Text)) {

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