This sample consists of a collection of CodeBehind files that demonstrates how to filter, sort and page data on the server.
This file demonstrates the basics of filtering data on the server by requesting filtered data and writing the filtered data into a textblock. Any server symbol that returns an array can be filtered.
To request filtered data, a command must be sent to the server that contains the orderBy property.
filter contains either a JSON object or a string which defines which array items are returned. This is done by defining a path to the property by which to filter, a comparator and a static value to compare against. Arrays can be filtered by the value of their items if they contain primitive data types like strings, numbers, or booleans by defining '{value}' as the path.
Valid comparators are:
'=='for strings, numbers and booleans'!='for strings, numbers and booleans'<'for numbers'>'for numbers'<='for numbers'>='for numbers'contains'for strings and arrays'contains not'for strings and arrays'== [ignore case]'for strings'!= [ignore case]'for strings'contains [ignore case]'for strings'contains not [ignore case]'for strings
Filters can be combined with and or or logic and can be nested to indicate precedence. Nested filters will be evaluated first.
To see this in action please take a look at the CodeBehindFiltering.ts file. This file contains examples for subscribing to and reading from a symbol using different filters. Remember to activate the SampleSymbols PLC to have access to the symbols used in the example.
This file demonstrates the basics of sorting data on the server by requesting sorted data and writing the sorted data into a textblock. Any server symbol that returns an array can be sorted.
To request sorted data, a command must be sent to the server that contains the orderBy property.
orderBy defines the criteria by which to sort and in which direction. This is done by defining a path to the property by which to sort and 'ASC' or 'DESC' for ascending or descending order. Arrays can be sorted by the value of their items if they contain primitive data types like strings, numbers, or booleans by defining '{value}' as the path.
For example to sort an array of numbers in ascending order (lowest first), use an orderBy value of '{value} ASC'. To access struct fields simply specify the fields name: 'myField DESC'. To access nested structs use 'myField::nestedValue ASC' and to access array items use 'myArray[2] DESC'.
To see this in action please take a look at the CodeBehindSorting.ts file. This file contains an example for subscribing to a symbol using sorting and reading from a symbol using sorting. Remember to activate the SampleSymbols PLC to have access to the symbols used in the example.
This file demonstrates the basics of paging a server symbol by requesting paged data and writing the paged data into a textblock. Any server symbol that returns an array can be paged.
To request paged data, a command must be sent to the server that contains one or both of the properties offset and limit.
offset defines the index of the first item that should be returned. For example an offset of 5 would lead to the first 5 items with indices 0-4 to be skipped while the 6th item with index 5 would be returned to the client.
limit simply defines how many items should be returned.
The server will send back the command, with its readValue containing the paged data. The command will also contain the property maxEntries, which specifies how many items the array holds in total. This can be used to calculate and display the number of pages.
To see this in action please take a look at the CodeBehindPaging.ts file. This file contains an example for subscribing to a symbol using paging and reading from a symbol using paging. Remember to activate the SampleSymbols PLC to have access to the symbols used in the example.
This file demonstrates how to combine filtering, sorting and paging in one request.
To request filtered, sorted and paged data, include the properties offset, limit, orderBy and filter in the request to the server.
To see this in action please take a look at the CodeBehindCombined.ts file. This file contains an example for subscribing to a symbol using filtering, sorting and paging. Remember to activate the SampleSymbols PLC to have access to the symbols used in the example.
The samples use symbols that are mapped to variables in the SampleSymbols PLC. If you want to run the samples you should activate that PLC project so the samples have access to the symbol values.