@BengangY I have made some corrections on a branch in my fork, could you please enable PRs on your fork so I can raise a PR to it. Alternatively you can just pull the top 3 commits from here https://github.com/kc284/xenadmin/commits/private/bengangy/CP-44371, but it is better if I could send a PR with comments to explain the changes.

This is one part of corrections, there are some more changes needed, but I didn't make them as they require greater code shifting so I'll leave it to you. Please see my other comments in this PR.

A general remark: normally for new controls we would add localized resx placeholders, but at the moment we have stopped shipping localized resources on master, so the palceholders are not needed. This is the first PR with missing placeholders, so please ensure it is merged after #3238 which disables the unit tests.

• If I enter an invalid value in one of the threshold cells (e.g. 120), and click the OK button, I get an error (little red icon in the cell). If I then change the value to something valid (e.g. 70) and click on a different cell, the little red icon should disappear, but it's still there.
• If I enter an invalid value in a cell in the last row, click to a different tab, then click the OK button, it takes me back to the NRPE page, which is correct, however, the row with the invalid value is out of view, one has to scroll down to see what's wrong. Ideally, the row containing the invalid cell should be selected or at least we should scroll into view. If there are more than one row with invalid cells, it should be at least the first invalid row in view.

• If I enter an invalid value in one of the threshold cells (e.g. 120), and click the OK button, I get an error (little red icon in the cell). If I then change the value to something valid (e.g. 70) and click on a different cell, the little red icon should disappear, but it's still there.

Updated. Now it will check when the datagridview lost focus each time.

• If I enter an invalid value in a cell in the last row, click to a different tab, then click the OK button, it takes me back to the NRPE page, which is correct, however, the row with the invalid value is out of view, one has to scroll down to see what's wrong. Ideally, the row containing the invalid cell should be selected or at least we should scroll into view. If there are more than one row with invalid cells, it should be at least the first invalid row in view.

Updated. Added a reselection process when error occurs. Code likes:

CheckDataGridView.CurrentCell = CheckDataGridView.Rows[0].Cells[0];
CheckDataGridView.CurrentCell = focusCellWhenErrorOccurs;

It will select the first row and then select the error row. The reason is that if it only selects the error row, if the user already selected the error row and scrolled down the datagrid and click to a different tab, then click the OK button, it will not focus on the error row. So it needs a switch process.

One more question: I noticed that when we disable NRPE and then we renable it, the previous settings are reset and the user has to set up thresholds again. Is this by design? (Asking because sometimes features do remember the settings when disabled).

I added a Thread.Sleep() for a few seconds within the Host.call_plugin() method to simulate what happens if, for example, we have a slow network and server requests take while to return. In this case, if I launch the dialog and click the NRPE page, I see an error pop-up:

Which means something is not working correctly if we click on the page while the NRPERetrieveAction is still in progress.

One more question: I noticed that when we disable NRPE and then we renable it, the previous settings are reset and the user has to set up thresholds again. Is this by design? (Asking because sometimes features do remember the settings when disabled).

By design, all the settings displayed in NRPE UI are retrieved from the host's configuration file when opening the dialog. If customers check 'enabled NRPE' and customize the setting, clicking 'OK' will rewrite the configuration file for each host, which means the previous settings won't be reset by following single-op like disable and re-enable. But there's actually one special case we can discuss, if customers modify thresholds together with checking 'disable NRPE', and then click the 'OK' button, the host will only disable the NRPE without rewriting the configuration file, so next time when enabling NRPE again, those changes won't be seen from UI.

I added a Thread.Sleep() for a few seconds within the Host.call_plugin() method to simulate what happens if, for example, we have a slow network and server requests take while to return. In this case, if I launch the dialog and click the NRPE page, I see an error pop-up:

Which means something is not working correctly if we click on the page while the NRPERetrieveAction is still in progress.

This is an issue caused by my removing the default values of the threshold in datagridview. I will fix it today.