StreamWriter invalidates web service cache: bug?

[BLUE]

I insert a string in cache in a property set and I retrieve that string in
the get.

I retrieve my string with Read web method and I insert it with Write web
method: to try cache I do Read, Write, Read.

When I do the second Read, string is null if in the property set,
before/after inserting data into cache I write this code:

using (StreamWriter streamWriter = new
StreamWriter(@"D:\Log.txt"))
{
streamWriter.Write(cacheValue);
streamWriter.Flush();
}

Debuggin the Write, in the watch windows I see the correct just inserted
value of cache.

The same behaviour persists if I write "Hello world" instead of cacheValue:
this deny to use cache in a web service where you need to write to a file!!!

It seems to be a bug since this behaviour is a nonsense!


Thanks,
Luigi.

 

[Mr. Arnold]

I insert a string in cache in a property set and I retrieve that string in
the get.

I retrieve my string with Read web method and I insert it with Write web
method: to try cache I do Read, Write, Read.

When I do the second Read, string is null if in the property set,
before/after inserting data into cache I write this code:

using (StreamWriter streamWriter = new
StreamWriter(@"D:\Log.txt"))
{
streamWriter.Write(cacheValue);
streamWriter.Flush();
}

Debuggin the Write, in the watch windows I see the correct just inserted
value of cache.

The same behaviour persists if I write "Hello world" instead of
cacheValue: this deny to use cache in a web service where you need to
write to a file!!!

It seems to be a bug since this behaviour is a nonsense!

Again, you should post to a dotnet.webservice NG that deals with Web service
issues, using VB, C# and C++ .NET. They have most likely been down the path
you're trying to go down.

 

[Jon Skeet [C# MVP]]

On Jun 14, 11:10 am, "BLUE" <blue> wrote:

The same behaviour persists if I write "Hello world" instead of cacheValue:
this deny to use cache in a web service where you need to write to a file!!!

It seems to be a bug since this behaviour is a nonsense!

This all sounds very unlikely. Could you post a short but complete
program which demonstrates the behaviour? See http://pobox.com/~skeet/csharp/complete.html
for what I mean by that.

Jon

 

[BLUE]

Finally I've found the error: if I try to write a file to bin dir (my desire
was to put all there to be tidy) the cache does not retain the values.

This is the code I used.



<%@ WebService Language="C#" Class="WS.MyWS" %>

using System;
using System.IO;
using System.Web.Services;
using System.Xml;

namespace WS
{
[WebService(Namespace="http://microsoft.com/webservices/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class MyWS: WebService
{
private DateTime LastUpdateDateTime
{
get
{
string path = this.Server.MapPath("bin\\File.txt");
DateTime utcNow = DateTime.UtcNow;
DateTime lastUpdateDateTime;
string cacheValue =
(string)this.Context.Cache["lastUpdateDateTime"];
if (cacheValue != null)
return XmlConvert.ToDateTime(cacheValue,
XmlDateTimeSerializationMode.Utc);

StreamReader streamReader = null;
try
{
streamReader = new StreamReader(path);
string s = streamReader.ReadToEnd().Trim();
// I want to see if cache value is taken so I comment
the following line
// lastUpdateDateTime = XmlConvert.ToDateTime(s,
XmlDateTimeSerializationMode.Utc);
lastUpdateDateTime = utcNow.AddYears(-7);
}
catch
{
File.Delete(path);
lastUpdateDateTime = utcNow.AddYears(-7);
}
finally
{
if (streamReader != null)
streamReader.Close();
}

return lastUpdateDateTime;
}
set
{
try
{
string cacheValue = XmlConvert.ToString(value,
XmlDateTimeSerializationMode.Utc);
this.Context.Cache["lastUpdateDateTime"] = cacheValue;

string path = this.Server.MapPath("bin\\File.txt");
using (StreamWriter streamWriter = new
StreamWriter(path))
{
streamWriter.Write(cacheValue);
streamWriter.Flush();
}
}
catch
{
}
}
}

[WebMethod]
public string Read()
{
DateTime dt = this.LastUpdateDateTime;
return XmlConvert.ToString(dt,
XmlDateTimeSerializationMode.Utc);
}

[WebMethod]
public void Write()
{
this.LastUpdateDateTime = DateTime.UtcNow;
}
}
}

 

[Jon Skeet [C# MVP]]

Finally I've found the error: if I try to write a file to bin dir (my desire
was to put all there to be tidy) the cache does not retain the values.

Right. I suspect ASP.NET thinks it's a change to your application, and
is recycling it (restarting the web app, basically).

Writing to the bin directory sounds like a bad idea anyway though.

Jon

 

[Mr. Arnold]

Finally I've found the error: if I try to write a file to bin dir (my
desire was to put all there to be tidy) the cache does not retain the
values.

One shouldn't write to the Bin directory or to wwwroot/appvirtual. It's a
security risk that a hacker can exploit. One reads a Web.config, App.config
or even a text.fle that has pathing pointing somewhere instead of anywhere
but the Web server itself on wwwroot.