To break completely out of a foreach loop (foregoing all the remaining loops), use: break;

To go to the next iteration in the loop, use: continue;

When is ‘break’ useful? It is particularly useful if you’re looping through an a collection of Objects (like Rows in a Datatable) and you’re searching for a particular match. When you find that match, there’s no need to continue through the remaining rows, so you want to Break out. There are plenty of other cases as well.

‘Continue’ is useful when you’ve accomplished what you need to in side a loop iteration and you don’t want to process the remaining code for that particular iteration. You’ll normally have ‘continue’ after an ‘if’.

Help for the DBNull Problem has Arrived!

The answer is so simple (at least in VS 2008 and greater, maybe before that too).  It is rather sad how much time I’ve wasted trying to deal with this problem.  Without further ado, the answer!

You’re probably using a Datarow object to get at the column values, probably buried in a foreach statement.  Instead of messing around with the specific column like  myRow.MyColumn, the Row object has an isNull method for each column in the row.  The method name takes the column’s name and puts “is” in front, and “null” behind.  So for a column called MyColumn, the method would be:   myRow.IsMyColumnNull();

Here’s a full example of dealing with nulls in a DateTime field. The logic is the same for Int or other numerics as well.

int iReq = 6196;
certdbTableAdapters.integration_procsTableAdapter taProcs = new certdbTableAdapters.integration_procsTableAdapter();
certdb.integration_procsDataTable dtProcs = taProcs.GetData(iReq);

certdb.integration_procsRow rowProc = dtProcs.Rows[0];

if(!rowProc.IsStartTimeNull())
{
    sProcDate = rowProc.StartTime.ToShortDateString();
}
else
{
    sProcDate = "";
}

The Craziness I Tried Before

Before I finally found the answer to this, I was using all sorts of crazy workarounds, including using multiple queries to be sure I never got a null situation, and using the fabulous Case statement within SQL statements. Here’s a little tast of a Case statement:

SELECT DISTINCT Process.ProcessID, Process.Name, Process.Description, Process.ResultLogStatusID,
Process.StatusTimeStamp, ResultLogStatus.Name AS ProcResult,
CASE WHEN LogProcess.EndTime IS NULL THEN '1/1/1900' ELSE LogProcess.EndTime END as rortime,
CASE WHEN LogProcess.Status IS NULL THEN 'missing' ELSE LogProcess.Status END as rorstatus
FROM         RequirementTestLink
LEFT JOIN Process ON Process.ProcessID = RequirementTestLink.ProcessID
LEFT JOIN ResultLogStatus ON Process.ResultLogStatusID = ResultLogStatus.ResultLogStatusID
LEFT JOIN LogProcess ON Process.ProcessID = LogProcess.ProcessID AND LogProcess.ResultOfRecord = 1 WHERE     (RequirementTestLink.RequirementID IN (" + sReqs + ")) ORDER BY Process.ProcessID

I tried lots of things…here are a couple others that didn’t work on my strongly typed datatables:

myRow.MyColumn != null
or
Convert.IsDBNull(myRow.MyColumn)

Neither worked! It’s a shame the answer was much simpler!

I hope this post will help someone else out there. Hopefully I’ll remember this post the next time I’m dealing with DBNulls.
Cheers,
Byron

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.

I looked and looked at this SQL code:

SELECT Process.ProcessID, Process.Name, Process.Description, Process.ResultLogStatusID, Process.StatusTimeStamp, ResultLogStatus.Name AS ProcResult, RequirementTestLink.RequirementID

FROM RequirementTestLink

LEFT JOIN Process ON Process.ProcessID = RequirementTestLink.ProcessID

LEFT JOIN ResultLogStatus ON Process.ResultLogStatusID = ResultLogStatus.ResultLogStatusID

WHERE (RequirementTestLink.RequirementID IN (" + sReqs + "))

ORDER BY RequirementTestLink.RequirementID, Process.ProcessID

It looked perfectly legit to me. I figured out that there would be multiple instances of Process.ProcessID in the RequirementTestLink table. But this shouldn’t have been a problem since it would just create multiple rows for the multiple instances.

Relax or turn off constraints in your DataSet.

The problem was that I was using a SQL Adapter to fill a DataTable. When I made the DataTable, it got junked up with Primary Key and Foreign Key constraints on the ProcessID field. The answer had been right there in the message (see image below). They spelled it out in the first line: “Relax or turn off constraints in your DataSet”. It took me 30 minutes to work it out on my own…if I’d just actually read those pop ups (but so often they are so cryptic I can’t comprehend them ).

So, to get rid of that Primary Key:

1. Left click on the key icon (you can see it in the image at right beside ProcessID)
2. Right click on the same key icon and select ‘Delete key’. 

If that doesn’t do it for you, then zap the Foreign Keys as well.  You can see one coming in at the top right (left picture).  Click on the line and delete it.