An expression is a perfect solution for most of the reports that we develop in real-time. But in some cases, we might need complex functionalities or calculations. In these situations, we can use the concept of Custom Code in SSRS.
SSRS Custom Code creates customized functions that incorporate in the report. Or create DLLs (Class libraries), so that we can reuse the same function in multiple reports.
In this article, we will show you the step by step approach to adding the custom code in SSRS report with a practical example
To demonstrate the steps involved in adding the Custom code in SSRS Report, We are going to use the previously generated report that we shown below. Please refer to Formatting Date and Time article to understand the SSRS report data.

Let me show you the report preview. As you can see, it is pretty ordinary Table Report with formatted date and time

How to add Custom Code in SSRS Report
To add the custom Code, we have to access the Report properties. And to do so, Right-click on the Empty space within the report designer will open the context menu. Please select the report properties option.

Or go to the Reports menu and select the Report Properties submenu as we showed below.

Either way, it will open the following window.

Please navigate yourself to the Code tab to write the custom code in a report.

Here, we are writing a simple function that will return the message “Welcome to Tutorial Gateway”. And the custom Code in SSRS is:
Function WelcomeMsg() As String return "Welcome to Tutorial Gateway" End Function

We have completed creating the function. Now let me use that function inside the report. To do so, add a TextBox to the Page Header.
Next, right-click on the Textbox will open the context menu. Please select the Expression option from it.

After you select the Expression option, a new window will open to write an expression. Here, write Code.WelcomeMsg (i.e., Code.FunctionName) and click OK.
Remember, the syntax to add the custom code is Code.Function_Name(Parameter1,….,ParameterN))

Now, let me show you the report preview after adding SSRS custom code. From the below screenshot, you can see the message that we created inside the function.

Next, let me add one more function to the Report properties code.
Function GreetingMsg() As String If (DateTime.Now.Hour < 12) Then Return "Good Morning Suresh" ElseIf (DateTime.Now.Hour < 17) Then Return "Good Afternoon Suresh" Else Return "Good Evening Suresh" End If End Function

Next, add the following code to the second TextBox in the page header

As you can see, we formatted the textBox

Let me show you the report preview after adding custom code in SSRS report
