ASP.NET MVC: dealing with Version field - asp.net-mvc

Question

I have a versioned model:
public class VersionedModel
{
public Binary Version { get; set; }
}
Rendered using
<%= Html.Hidden("Version") %>
it gives:
<input id="Version" name="Version" type="hidden" value=""AQID"" />
that looks a bit strange. Any way, when the form submitted, the Version field is always null.
public ActionResult VersionedUpdate(VersionedModel data)
{
...
}
How can I pass Version over the wire?
EDIT:
A naive solution is:
public ActionResult VersionedUpdate(VersionedModel data)
{
data.Version = GetBinaryValue("Version");
}
private Binary GetBinaryValue(string name)
{
return new Binary(Convert.FromBase64String(this.Request[name].Replace("\"", "")));
}

Answer 1

Related posts I found.
Link
Suggests to turn 'Binary Version' into 'byte[] Version', but some commenter noticed:
The problem with this approach is that
it doesn't work if you want to use the
Table.Attach(modified, original)
overload, such as when you are using a
disconnected data context.
Link
Suggests a solution similar to my 'naive solution'
public static string TimestampToString(this System.Data.Linq.Binary binary)
{ ... }
public static System.Data.Linq.Binary StringToTimestamp(this string s)
{ ... }
http://msdn.microsoft.com/en-us/library/system.data.linq.binary.aspx
If you are using ASP.Net and use the
SQL Server "timestamp" datatype for
concurrency, you may want to convert
the "timestamp" value into a string so
you can store it (e.g., on a web
page). When LINQ to SQL retrieves a
"timestamp" from SQL Server, it stores
it in a Binary class instance. So you
essentially need to convert the Binary
instance to a string and then be able
to convert the string to an equivalent
Binary instance.
The code below provides two extension
methods to do this. You can remove the
"this" before the first parameter if
you prefer them to be ordinary static
methods. The conversion to base 64 is
a precaution to ensure that the
resultant string contains only
displayable characters and no escape
characters.
public static string ConvertRowVersionToString(this Binary rowVersion) {
return Convert.ToBase64String(rowVersion.ToArray());
}
public static Binary ConvertStringToRowVersion(this string rowVersion) {
return new Binary(Convert.FromBase64String(rowVersion));
}

Answer 2

I think the problem with not seeing it in the bound model on form submission is that there is no Convert.ToBinary() method available to the model binary to restructure the data from a string to it's binary representation. If you want to do this, I think that you'll need to convert the value by hand. I'm going to guess that the value you are seeing is the Base64 encoding of the binary value -- the output of Binary.ToString(). In that case, you'll need to convert it back from Base64 to a byte array and pass that to the Binary() constructor to reconstitute the value.
Have you thought about caching the object server-side, instead? This could be a little tricky as well as you have to detach the object from the data context (I'm assuming LINQ) or you wouldn't be able to reattach it to a different data context. This blog entry may be helpful if you decide to go that route.

Answer 3

You may need to use binding to get a strongly-typed parameter to your action method.
Try rendering using:
<%=Html.Hidden("VersionModel.Version")%>
And defining your action method signature as:
public ActionResult VersionedUpdate([Bind(Prefix="VersionModel")] VersionedModel data)
{
...
}

Answer 4

This post http://forums.asp.net/p/1401113/3032737.aspx#3032737 suggests to use
LinqBinaryModelBinder from http://aspnet.codeplex.com/SourceControl/changeset/view/21528#338524.
Once registered
protected void Application_Start()
{
ModelBinders.Binders.Add(typeof(Binary), new LinqBinaryModelBinder());
}
the binder will automatically deserialize Version field
public ActionResult VersionedUpdate(VersionedModel data)
{ ... }
rendered this way:
<%= Html.Hidden("Version") %>
(See also http://stephenwalther.com/blog/archive/2009/02/25/asp.net-mvc-tip-49-use-the-linqbinarymodelbinder-in-your.aspx)

Answer 5

There are many ways like here
byte[] b = BitConverter.GetBytes(DateTime.Now.Ticks);//new byte [(DateTime.Now).Ticks];
_store.Version = new System.Data.Linq.Binary(b)
(make sure you bind exclude your version),
But the best way is to let the DB handle it...

Answer 6

There are many ways like here
byte[] b = BitConverter.GetBytes(DateTime.Now.Ticks);//new byte [(DateTime.Now).Ticks]; _store.Version = new System.Data.Linq.Binary(b)
(make sure you bind exclude your version),
But the best way is to let the DB handle it...