Using Variables

LINQ Reporting Engine enables you to use variables in template documents. Variables are useful when you need to calculate an expensive value just once and access it multiple times in a template. Also, calculation of complex values such as running (progressive) totals may require variables, see “Appendix C. Typical Templates” to get an example.

You can declare a variable in a template using a var tag as follows.

<<var [variable_type variable_name = variable_value]>>

The following table describes elements of the var tag.

Element	Optional?	Remarks
Variable Type	Yes	You can specify the type of a variable explicitly. This type must be known by the engine (see “Setting up Known External Types” for more information). If you do not specify the type explicitly, it is determined implicitly by the engine from the specified variable value.
Variable Name	No	For a new variable, its name must be a unique identifier.
Assignment Operator	No
Variable Value	No

During runtime, a var tag is removed while the value of the corresponding variable is calculated and set appropriately.

After a variable is declared in a template, its value can be accessed using the name of the variable as any other identifier. For example, the following template outputs string “Hello!”

<<var [s = “Hello!”]>><<[s]>>

You can redefine the value of a variable using a var tag against the name of this variable. For example, the following template outputs string “Hello, World!”

<<var [s = “Hello, ”]>><<[s]>><<var [s = “World!”]>><<[s]>>

Using of variables has the following restrictions:

• You can not redefine the type of a variable.
• You can not use the contextual object member access feature against a variable. See “Using Contextual Object Member Access” for more information.
• Using a var tag, you can not redefine the value of an iteration variable or a data source.