SSRS: Custom Code and Expressions

 Custom code and expressions in SSRS (SQL Server Reporting Services) provide powerful ways to extend the functionality of your reports, enabling dynamic behavior, complex calculations, and custom formatting. Here’s a detailed look at both aspects:

Custom Code in SSRS

Custom Code can be written in Visual Basic (VB) and embedded directly in a report. This allows you to create reusable functions and procedures that can be called from expressions within the report.

Adding Custom Code

1. Open Report Properties: In the report designer, right-click on the design surface outside the report area and select "Report Properties."
2. Add Code: Go to the "Code" tab and enter your VB code. Example:

   vb
   
   Public Function FormatCurrency(ByVal amount As Decimal) As String
       Return "$" & Format(amount, "N2")
   End Function
   

Using Custom Code in Expressions

To use the custom code in an expression:

1. Expression Dialog: Open the expression dialog by right-clicking on a textbox or other report item and selecting "Expression."
2. Call the Function: Use Code.FunctionName. Example:

   vb
   
   =Code.FormatCurrency(Fields!SalesAmount.Value)
   

Expressions in SSRS

Expressions are used extensively throughout SSRS to set properties, calculate values, and create dynamic behavior. They are written in VB and can reference report items, fields, parameters, and built-in functions.

Common Uses of Expressions

1. Dynamic Text: Setting the value of a textbox based on data or parameters.

   vb
   
   ="Sales Report for " & Parameters!ReportDate.Value
   

2. Conditional Formatting: Changing the appearance of report items based on data values.

   vb
   
   =IIf(Fields!Sales.Value > 1000, "Green", "Red")
   

3. Aggregations: Performing calculations such as sums, averages, and counts.

   vb
   
   =Sum(Fields!Sales.Value)
   

4. String Manipulation: Concatenating strings, extracting substrings, and formatting.

   vb
   
   =Left(Fields!ProductName.Value, 10)
   

5. Date Functions: Manipulating and formatting dates.

   vb
   
   =Format(Fields!OrderDate.Value, "MM/dd/yyyy")
   

6. Math Functions: Performing mathematical calculations.

   vb
   
   =Fields!Quantity.Value * Fields!UnitPrice.Value
   

Advanced Expression Examples

1. Complex Conditional Formatting:

   vb
   =IIf(Fields!Sales.Value > 1000, "Green", IIf(Fields!Sales.Value > 500, "Yellow", "Red"))
   Custom Aggregates:

2. vb
   
   =RunningValue(Fields!Sales.Value, Sum, "DataSet1")
   

3. Multi-Line Text:

   vb
   ="Customer: " & Fields!CustomerName.Value & vbCrLf & "Order Date: " & Format(Fields!OrderDate.Value, "MM/dd/yyyy")
   
   

Tips for Using Custom Code and Expressions

1. Keep It Simple: While custom code can be powerful, keep it as simple as possible to avoid maintenance difficulties.
2. Test Thoroughly: Ensure that your custom code and expressions work correctly by thoroughly testing them with various data scenarios.
3. Use Built-In Functions: Leverage SSRS's built-in functions and capabilities before resorting to custom code.
4. Performance Considerations: Be mindful of performance, especially when using complex expressions or custom code that runs for every row in a large dataset.

Troubleshooting Common Issues

1. Syntax Errors: Double-check your VB syntax, as even minor mistakes can cause errors.
2. Debugging: Use temporary textboxes to display intermediate values and debug your expressions.
3. Scope: Ensure that your aggregations and running values are using the correct scope.

By mastering custom code and expressions in SSRS, you can create highly dynamic and sophisticated reports that meet complex business requirements.