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Tuesday, October 23, 2012

A Known Error in WCF Restful Service

I found a resolution of a commonly occurring error while working with WCF restful services and I copied the entire problem description and its resolution from this blog.

The text reads as below

A little while ago I ran into an interesting set of errors that may be of interest to you. Consider the following service contract snippet:
String GetData(String value);

If you add the enableWebScript behavior to an endpoint that is using the WebHttpBinding, you will see this exception when the ServiceHost starts:

System.InvalidOperationException: Endpoints using 'UriTemplate' cannot be used with 'System.ServiceModel.Description.WebScriptEnablingBehavior'.

The reason for this error is rooted in the origin of the enableWebScript behavior. One of it's design objectives was to simplify working with the ASP.NET AJAX stack (Javascript proxy, JSON messages, etc). The AJAX stack doesn't have the equivalent of the UriTempalte type. It simply puts parameters in query strings (gets) and constructs entity bodies (posts). This is the default behavior of the WCF stack when the WebGet / WebInvoke annotations do not have a value for UriTemplate. Since any value of UriTemplate would be incompatible with the ASP.NET AJAX stack, we throw when it's present.

If you want JSON messages from a contract and you want to use the UriTemplate niceness, you can change your contract to:
[WebGet(UriTemplate="foobar/{value}", ResponseFormat=WebMessageFormat.Json)]
String GetData(String value);

Then, instead of using the enableWebScript behavior, use the WebHttpBehavior. You'll lose compat with the ASP.NET AJAX client stack (and the JS proxy), but you have the URI you are looking for.

The same is true if you are using the WebInvoke attribute and any HTTP method other than POST. The AJAX client stack only knows GET and POST... 

Thursday, October 4, 2012

SQL:Finding occurance of chars/words in String

The following is a very simple logic to check the ocuurance of chars/word in a larger string. This thing is particularly important when you want to just check if the string that you are searching for occurs as a sub-string of a value in a larger string which may be a value of a column in a table.

One practicle example would be say for example you want to check if a role is there in a column of user_roles which has a comma separated value of all roles for a particular user, so here you know what you have to look for in a column of all roles.

DECLARE @FindSubString VARCHAR(MAX)SET @LongSentence = 'My Super Long string with long words'SET @FindSubString = 'long'SELECT (LEN(@LongSentence) - LEN(REPLACE(@LongSentence, @FindSubString, ''))) CntReplacedChars,(
LEN(@LongSentence) - LEN(REPLACE(@LongSentence, @FindSubString, '')))/LEN(@FindSubString) CntOccuranceChars

In simple terms all it does is

Length of Long Seq (36) minus Length of Long Sentence with all 'long' replaced with blank (24) = 8 so we have 8 ocurrences of the characters

The above divided by the Length of 'long' will give you the occurrences of the word 'long' in the Long Sentence i.e 2

or 8/4 = 2

**I got the above T-SQL from this source

Wednesday, September 26, 2012

Adding System.ServiceModel.Web.dll in v4.0

While creating a WCF service library on Visual Studio 2010, I am sure many of you have faced an issue where you are not able to find the System.ServiceModel.Web.dll.

The reason being that Visual Studio by default targets the 4.0 Client Profile and System.ServiceModel.Web.dll is not present in that list of libraries to be referenced. The work around is to change the target framework to v.4.0 instead of the 4.0 Client profile.

* The same problem will not arise if you have created a WCF Service Application.

Sunday, August 19, 2012

WCF Base Address error on Windows Vista

I am sure its not only me but many of you have encountered an unusual error when you first started an instance of a WCF Host application through Visual Studio on Windows Vista, the error will look something like this below

{"HTTP could not register URL http://+:49779/WcfServiceLibraryNorthwind/NorthwindService/. Your process does not have access rights to this namespace (see for details)."}

Since vista's security is not exactly like old windows, so the owner of an HTTP namespace (in this case the administrator) will have to delegate that ownership to another user, so the command would be something like this below

"netsh http add urlacl url=http://+:portNumber/ user=MYMACHINE\UserName"

i.e as below in my case
netsh http add urlacl url=http://+: 49779/ user=KAUSHIK-PC\Kaushik

*On success, you will get a message like below
URL reservation successfully added

** please open the command shell "As Administrator", otherwise you will get an error as below 

Url reservation add failed, Error: 5