Custom Functions

Custom functions

There are about 100 common functions in SSRS 2005, and they can handle most of what you will need to do. Occasionally, however, you will still need to set an expression with more control than the common functions can manage. So, to make SSRS even more flexible, you can write custom VB.NET or C# functions and use them in expressions.

Open the report and navigate to the Layout tab. From the Report menu select Report Properties and then jump to the Code tab.

We are going to write a custom function that returns a different color, depending on the value that is passed to it. We will then use that function to set the background color for the status field in the report detail table.
Copy the following code into the code window:
        Public Function GetColor(ByVal status as String) as String
            IF status = "1" Then
                Return "White"
            End IF
            IF status = "2" Then
                Return "Yellow"
            End IF
            IF status = "3" Then
                Return "Tomato"
            End IF
        End Function
Click OK and close the window.

Now that we have a function that returns color names we need to wire up that function to an expression.
Click on the Customer Status cell and open the Properties window. Find the Background Color property and choose Expression from the dropdown. Add the following line of code to create an expression:
=code.GetColor(Fields!ChStatus.Value)
When the report runs and this expression is resolved, SSRS will call your GetColor function and pass the value of the customer status for that instance of the row to the function. The function takes over and decides which color should be returned. SSRS then uses that value as the value for the background property for that cell.
Please note that custom functions must be called using =code.<myfunction>.
Now navigate to the Preview tab and run the report..