Steve Sloka

Linq -- SubmitChanges() not saving to database

monkey9987 — Tue, 08 Sep 2009 17:18:00 GMT

I've been working with Linq now for a while, but sometimes the simplest things get the best of you. I was working with a new project where I had been using Linq all over the place. Everything was working, selecting rows, inserting logs, etc, etc, however, one portion was not. I was attempting to get a row from the database, changing a value then saving back that row.

Here's an example:

DataContext db = new DataContext(pConnectionString);
MyRow pRow = db.MyRows.SingleOrDefault(p => p.pkID == ppkID);
pRow.column = DateTime.Now;
db.SubmitChanges();

Looked good to me. So I did some digging through my database and found that for some reason I did not set a Primary Key on the table I was trying to update. There aren't any exceptions or errors thrown so it was a little more hidden.

So to summarize, make sure you set your primary keys when using linq, even if it needs to be a surrogate key!

~ Steve

VS2008 Performance

monkey9987 — Mon, 28 Jan 2008 18:26:00 GMT

I have been having some performance problems with Visual Studio 2008 web applications. I see a delay when working on aspx pages. Just typing, adding controls, or switching between Design to Code view (or even Split) would spike the cpu a little and freeze up for 10-15 seconds.

I found this forum post which fixed my issue completely. It seems to be related to the HTML validation.

Here's the change which worked for me:

Tools --> Options --> Text Editor --> HTML --> Validation and clear the 'Show errors' checkbox to completely disable any HTML validation at all.

~ Steve

LINQ to DataTable

monkey9987 — Mon, 28 Jan 2008 16:54:00 GMT

We have been adopting Linq slowly but surely and have run into some issues we never had to deal with in the past. Currently I use DataSets in VS2005 for everything. These are nice since they return DataTables easily and allow updates / inserts / etc without issue.

When we dove into Linq and had to return a DataTable for the first time we were stuck. Looking through examples & searching online did not return much. I did find an example by Kevin Goff in CoDe Magazine which outlined 13 tips for Linq. This worked great except I had some issues with null datatypes. Those issues should be fixed in the sample below.

The following code outlines a quick way using Linq to query a database and return the results to a DataTable.

Here is my newly created class:

static public class ConvertDataTable

{

public static DataTable ToADOTable<T>(this IEnumerable<T> varlist, CreateRowDelegate<T> fn)

{

DataTable dtReturn = new DataTable();

// Could add a check to verify that there is an element 0

T TopRec = varlist.ElementAt(0);

// Use reflection to get property names, to create table

// column names

PropertyInfo[] oProps =

((Type)TopRec.GetType()).GetProperties();

foreach (PropertyInfo pi in oProps)

{

Type colType = pi.PropertyType;if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))

{

colType = colType.GetGenericArguments()[0];

}

dtReturn.Columns.Add(new DataColumn(pi.Name, colType));

}

foreach (T rec in varlist)

{

DataRow dr = dtReturn.NewRow();foreach (PropertyInfo pi in oProps)
{
dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue(rec, null);
}

dtReturn.Rows.Add(dr);

}

return (dtReturn);

}

public delegate object[] CreateRowDelegate<T>(T t);

}

Here is the usage in code:

LData.MyDataContext db = new LData.MyDataContext(); var query = from p in db.Extensions
where p.DepartmentNumber == "412"select p;

DataTable dt = query.ToADOTable(rec => new object[] { query });

Hope this helps someone else out.

~ Steve

New Blog!

monkey9987 — Wed, 23 Jan 2008 16:59:00 GMT

I responsed to Joe's post on getting a new blog setup on asp.net here we are.

I work for a Software company 20 minutes outside of Pittsburgh, PA. We develop communications based software which integrates into systems like AVAYA, & Cisco. We heavily use ASP.NET, SQL 2005, Reporting Services, and Winforms in a day-to-day operations in the software we sell. We also do a fair amount of .NET remoting.

More details to come!

~ Steve