Calling a Custom External Assembly from a Report

One of the most powerful features of Reporting Services is the ability to call code from within a report. Before we get to that, you may or may not know you can call the .net Framework from within the expression of an objects property on a report. However, there is one rule you must follow, the code must be written in VB.Net.

  • For example: 
    =iif( me.Value < 0, “Red“, “Black“) placed in the color property of a textbox this expression will change the text colour based on the value returned.
    =Format(Fields!BirthDate.Value, "MMM dd,yyyy") placed in the value property this expression will format a date value, (ie Dec 10, 2006)=System.Web.HttpContext.GetGlobalResourceObject("AppResources", "ID14831").ToString() placed in the value property uses your existing resource file to translate a label

Although this is all great and very useful, if you need to do something a bit more complicated you can write your own code and call that from an expression in a report also. This can be done in two ways.

1. You can write code directly in the report using the report properties Code tab. The code tab contains a multi-line textbox where you can write code that can be called from the expressions of the report. From the menu select Report - Report Properties... on the Report properties dialog select the Code Tab. Here you can write code like in the example below. Once again it must be VB.Net.

To use this code in your report place the following into the Value proprty of the textbox where you want to display the Pay Frequency.  


2. You may want to reuse the code you write, across many reports. if that is the case, first write your assembly in the .net language of your choice. Then make sure the assembly is in the correct folder so it can be found by the Report Server and the Report Designer. I have a Blog entry here to help you with that.

Now you need to create a reference to the Assembly from the report. There is a reference tab on the Report properties dialog. Make sure you put the namespace in front of the class name or it won't work.

Now you can call your Assembly from any expression by referencing the class and method in the expression. Like this: