I like a lot of the built in features the built-in DataSet designer provides in VS2010 and do not want to have to change to something entirely different if at all possible. The problem is, to have optional parameters, I need to create completely independent functions for each combination of parameters. So for 6 parameters, I would need 63 different functions. That's obviously completely unmanageable.
Is there a way to have one function which ONLY adds a parameter to the generated WHERE clause of my SQL if it has a value, and otherwise, it ignores it?
You could add these optional paremeters into the WHERE-Clause with ISNULL:
WHERE (YourTable.Column = ISNULL(#Column, YourTable.Column))
On this way the SQL works with or without the (optional) parameter. If the value is null it won't affect the result.
You only have to add all parameters into the DataAdapter's parameter-collection(the optional with AllowDbNull=true). But i'm fairly sure that they will be automatically added correctly.
Related
I am trying to learn Servlet annotations and came across this snippet
#WebServlet(urlPatterns="/MyPattern", initParams={#WebInitParam(name="ccc", value="333")})
This makes sense to me. However, I don't understand why it is not like this
#WebServlet(urlPatterns="/MyPattern", initParams={(name="ccc", value="333"), (name="abc", value="1")})
So, the question is why we need to put #WebInitParam annotation when we already declared the attribute as initParams. It seems redundant to me, or am I missing something?
The alternative you suggest would not even compile.
When you look at the JLS, it states this:
It is a compile-time error if the return type of a method declared in
an annotation type is not one of the following: a primitive type,
String, Class, any parameterized invocation of Class, an enum type
(§8.9), an annotation type, or an array type (§10) whose element type
is one of the preceding types.
So in order to group name and value together, which represent the initialization parameter the only option is to use annotation (#WebInitParam in this case) with corresponding values set as its parameters.
As with most questions about language design choices we can only speculate here. I think some reasons for this are:
Keeping the language simple.
It is kind of redundant, but the syntax for annotations can be reused and does not require new language constructs. This makes it easier to parse and to read. Sure, It's longer, but it's also more explicit to write the annotation's name.
Don't restrict possible future language enhancements.
The proposed syntax would not work if annotations would support inheritance. I don't know if that's even a planned feature but it would not be possible to implement straightforward it if the type can be omitted.
In many cases an array of annotations seems like a workaround anyway. It can be avoided in Java 8, where you can add multiple annotations of the same type:
#WebServlet(urlPatterns="/MyPattern")
#WebInitParam(name="ccc", value="333")
#WebInitParam(name="abc", value="1")
(I don't know if the servlet api actually supports this yet though)
Intro: I'm writing web interface with SQLAlchemy reflection that supports multiple databases. It turns out that authors of application defined postgresql with lowercase tables/columns, eg. job.jobstatus while sqlite has mixed case, eg Job.JobStatus. I'm using DeclarativeReflectedBase from examples to combine reflection and declarative style.
The issue: Configure SQLAlchemy to work with tables/columns case insensitive with reflection
I have done so far:
I have changed DeclarativeReflectedBase.prepare() method to pass quote=False into Table.__init__
What is left to be solved:
relationship definitions still has to obey case when configuring joins, like primaryjoin="Job.JobStatus==Status.JobStatus".
configure __tablename__ based on engine type
The question: Are my assumptions correct or is there more straightforward way? Maybe I could tell reflection to reflect everything lowercase and all problems are gone.
you'd probably want to look into defining a ".key" on each Column that's in lower case, that way you can refer to columns as lower case within application code. You should use the column_reflect event (See http://docs.sqlalchemy.org/en/latest/core/events.html#schema-events) to define this key as a lower case version of the .name.
then, when you reflect the table, I'd just do something like this:
def reflect_table(name, engine):
if engine.dialect.name == 'postgresql':
name = name.lower()
return Table(name, autoload=True, autoload_with=engine)
my_table = reflect_table("MyTable", engine)
I think that might cover it.
Is it possible to create a new array in windows workflow? More specifically, in the designer.
I've created a variable of System.Int32[], but when I use it I get a NullReferenceException.
I've tried New Int32(5), and various permutations of Dim - nothing I have tried has worked.
I was able to create the array and pass it as an in/out parameter - this works, however the workflow will need to determine the actual size of the array.
To create and instantiate an array, you have to set a default value to your variable with New Int32(FOO SIZE){} or use an Assign activity to instantiate it with the correct size in runtime
You can also use List(Of T) or any other .NET collection structure to achieve dynamic size.
Note that the value must be the right part of a set expression. So, you can google how to do it in VB.NET and you will be fine.
I assume that if you are creating the array in the designer, as you stated, it is either a workflow variable or a workflow argument. The "WF" way to do this would be to use the "Default Value" column under the "Variables" and/or "Arguments" tab.
If it is an argument then the Default Value column only works if the Direction is "In". If your argument is a property, or an Out, or In/Out direction then you would have to use the method mentioned by Davi.
If you are creating it under the "Variables" tag then using the Default value column would be the more built-in approach. The syntax in the default column would be the same syntax mentioned by Davi: New Int32(FOO SIZE) {}
I'm currently using Drupal Views 2 to build custom views. This works fine so far, if there wasn't a feature needed: One should be able to filter the results by different fields via URL, in the form of:
http://domain/node/M/[key]:[value],[key2]:[value2],...,[keyN]:[valueN]
The key names are fixed and may not be altered.
I tried hooking hook_views_query_alter() and hook_views_pre_render() to generalize this for all views, evaluating the given filterset, but to no satisfying end, as i could not get hold of the query used to build the view (I could not alter it in the proper way, as i do not know the field names in the query).
The question is, if there is a nicer way to implement such a filterset.
thanks in advance,
flo
Looking at the comments you seem to want not only url arguments but url arguments in a custom format.
I would firstly urge you to drop your format and use the standard views argument format, this will be more standards compliant and save you a lot of headache.
If you want to use that paticular format you are going to have to write some custom code in a module.
Register a callback using hook_menu().
In that callback use arg() and decode your arguments.
Pass the arguments to views_embed_view(). as shown here
In a legacy MFC CHttpServer based web server, we have a command parsing map something like this:
BEGIN_PARSE_MAP(MyHttpServer, CHttpServer)
ON_PARSE_COMMAND(MyPage, MyHttpServer, ITS_I4 ITS_I4 ITS_I4 ITS_I4 ITS_PSTR ITS_PSTR ITS_PSTR ITS_I4)
ON_PARSE_COMMAND_PARAMS("intParam1=11 intParam2=12 intParam3=13 intParam4=14 strParam5=s5 strParam6=s6 strParam7=s7 intParam8=18")
END_PARSE_MAP(MyHttpServer)
This defines a page accessible at http://host/path/dllname.dll?MyPage that accepts up to 8 parameters named intParam1, intParam2, intParam3, intParam4, strParam5, strParam6, strParam7, and intParam8.
The calling applications can invoke the page with the parameters in a named fashion like this:
http://host/path/dllname.dll?MyPage?intParam4=32&strParam7=somestring
But the way MFC command parsing maps work, they can also call it with unnamed parameters as long as they are provided in the order defined by the map:
http://host/path/dllname.dll?MyPage?21&22&23&24&string5&string6&string7&28
I would like to replace this old code with an ASP.Net page, but we have existing calling applications that will not be changed that invoke the page using both styles of parameter passing, named and unnamed.
I can easily manage the necessary URL rewriting to allow an ASP.Net page to respond to the URL as given above, replacing the path/dllname.dll? MyPage portion with the path to an .aspx page or .ashx handler.
The problem comes in when trying to handle the unnamed parameters in an equivalent fashion to the old MFC parameter parser. Request.QueryString treats all the unnamed parameters as being named with null and Request.QueryString[null] returns a comma-separated list of the values. This is pretty close to workable, but should one of the parameters actually contain a comma, this encoding falls apart because the extra comma is not escaped and splitting the string on the commas will end up with too many parameters.
In classic ASP, I believe Request.QueryString(...) returned a collection of all the parameters that were identically named. There seems to be no equivalent to that in ASP.Net that I can find.
As a secondary issue, the MFC command parsing map had some pretty convoluted logic for dealing with a mixture of named and unnamed parameters. Although the callers of the page in question will not be mixing their usage in this way, I am interested in perhaps duplicating the logic for completeness sake. Can anyone confirm that MFC's behavior was essentially the following?
Process all parameters in the URL from left to right, using & as separator.
If named (has an equal sign), apply the value to the parameter with the corresponding name, regardless of its position. If that parameter already assigned a value, error.
If unnamed, apply the value to the parameter at the nth position in the command parsing map, where n is the number of already processed unnamed parameters plus 1. If that parameter was already assigned a value, error.
Apply default values from command parsing map to any parameters not assigned above
If any parameters from command parsing map have not been assigned a value, error.
One more interesting note, it appears that Request.QueryString.ToString() will nearly reconstitute the original parameters on the URL, but it always moves the parameters with identical names to be together, including the unnamed parameters I am concerned with here.
Not sure if solves your problem, but you could try using Request.PathInfo. This will give you everything entered after the page, which you could then parse manually using something like a regex.
For example, if you had the URL:
http://host/path/dllname.dll?MyPage?21&22&23&24&string5&string6&string7&28
The Request.PathInfo property would return:
?MyPage?21&22&23&24&string5&string6&string7&28
Processing this into a set of values that you can work with could also be problematic as you've got both named and un-named parameters, but this should be achievable using regular expressions and/or splitting the string.
I found that Request.QueryString has a GetValues() method. This returns an array of strings and solves the problem of a comma being embedded within one of the values. It'll be even easier to use than having to split the results of Request.QueryString[null].
I still have a bit of work to use this to implement an MFC-like mapping of URL parameters that handles both named and unnamed parameters.