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Report parameters
=================

You can specify the parameters of the report. For example, the 
**Customer purchases** report of the Demo project have three parameters.

.. image:: /programming/_images/parameters.png
	:align: center
	:alt: Report parameters

To add or change a report parameter click **Report params** button in the left 
panel of Administrator. A form will appear displaying the list of existing 
parameters. Then click New or Edit button of the form to add or change the
parameter.

.. image:: /programming/_images/report_param.png
	:align: center
	:alt: Report param

In the dialog box fill in:

* **Caption** - the name of the parameter that appears to users

* **Name** - the name of the parameter will be used in programming code to get 
  access to the parameter object.
  
* **Type** - the data type of the parameter

* **Visible** - the client application creates a form to specify the parameters 
  before printing the report. If this checkbox is checked, the input element for 
  this parameter will appear in the form

* **Required** - if this checkbox is checked and **Visible** attribute is set, 
  the client application will require a users to specify the parameter value 
  before printing the report

* **Align** - specifies how a value of the parameter will be aligned in the 
  input element
  
You can create a lookup parameter, For example, the **Customer purchases** 
report has a **Customer** parameter that can be selected from **Customers** 
catalog:

.. image:: /programming/_images/lookup_param.png
	:align: center
	:alt: Lookup parameter

In this case you should specify 

* **Lookup item** - the item to select the parameter value from

* **Lookup field** - the field in the lookup item

Form for setting the parameters of **Customer purchases** report is as follows:


.. image:: /programming/_images/customer_purchases_params.png
	:align: center
	:alt: Customer purchases parameters example

