Overview
Developing custom code stages or actions within Blue Prism is a powerful way to extend the capabilities of the software beyond its standard features. This skill is crucial for complex automation projects that require functionalities not available out-of-the-box in Blue Prism. Custom code stages allow developers to integrate external libraries, interact with APIs, perform complex data manipulation, and much more, thereby enhancing the automation’s capabilities and efficiency.
Key Concepts
- Custom Code Stage: A feature in Blue Prism that allows developers to write and execute custom code (C# or VB.NET) directly within a process.
- Integration with External Libraries: Utilizing custom code to extend Blue Prism functionalities by incorporating external .NET libraries or APIs.
- Error Handling: Implementing robust error handling within custom code to ensure the stability and reliability of the automation process.
Common Interview Questions
Basic Level
- What is a custom code stage in Blue Prism, and why is it used?
- How do you add and reference external libraries in a Blue Prism custom code stage?
Intermediate Level
- Can you explain how you would implement error handling within a custom code stage?
Advanced Level
- Discuss a complex scenario where you optimized a Blue Prism process using a custom code stage. How did it improve the process efficiency?
Detailed Answers
1. What is a custom code stage in Blue Prism, and why is it used?
Answer: A custom code stage in Blue Prism is a feature that allows developers to write and execute custom code (C# or VB.NET) within a process or object. This capability is used to extend the functionality of Blue Prism by enabling complex data manipulations, integrations with external systems or APIs, and implementing logic that is not directly supported by Blue Prism's built-in stages.
Key Points:
- Enables the use of .NET languages to extend functionality.
- Allows integration with external systems and APIs.
- Facilitates complex data manipulation.
Example:
// Example of a simple custom code stage that adds two numbers
int number1 = 5; // Assume these inputs are passed from Blue Prism
int number2 = 10;
int sum = number1 + number2;
// The sum would then be returned to Blue Prism
2. How do you add and reference external libraries in a Blue Prism custom code stage?
Answer: To add and reference external libraries in a Blue Prism custom code stage, you must first ensure the DLL file of the library is accessible to Blue Prism. This typically involves placing the DLL in a directory that Blue Prism can access (e.g., its installation directory or a specified path in the system environment). You then reference the library directly in your custom code stage using the using directive for C# or Imports for VB.NET, and ensure that the namespaces and classes from the library are correctly referenced in your code.
Key Points:
- Place the DLL in an accessible directory.
- Use using or Imports to reference the library in your code.
- Ensure correct referencing of namespaces and classes.
Example:
// Assuming Newtonsoft.Json.dll is added and accessible
using Newtonsoft.Json;
public void ConvertObjectToJson()
{
var person = new { Name = "John", Age = 30 };
string json = JsonConvert.SerializeObject(person);
// json contains the serialized JSON string of the person object
}
3. Can you explain how you would implement error handling within a custom code stage?
Answer: Implementing error handling within a custom code stage involves using try-catch blocks to catch exceptions that may occur during the execution of the custom code. It's important to catch specific exceptions to handle known error conditions gracefully and use a general catch block for unexpected exceptions. Additionally, logging the error details and setting output parameters to inform the Blue Prism process of the error are crucial steps.
Key Points:
- Use try-catch blocks for exception handling.
- Catch specific and general exceptions.
- Log error details and set output parameters for Blue Prism.
Example:
try
{
// Attempt risky operation
int result = 10 / 0; // This will cause a DivideByZeroException
}
catch (DivideByZeroException ex)
{
// Handle specific known error condition
Console.WriteLine("Cannot divide by zero.");
}
catch (Exception ex)
{
// Handle unexpected errors
Console.WriteLine($"An unexpected error occurred: {ex.Message}");
}
4. Discuss a complex scenario where you optimized a Blue Prism process using a custom code stage. How did it improve the process efficiency?
Answer: A complex scenario involved optimizing a Blue Prism process that required data transformation and communication with a REST API. The initial implementation used multiple stages with loops and data items, which was inefficient and slow. By implementing a custom code stage, I was able to use the HttpClient class to efficiently handle HTTP requests and Newtonsoft.Json for parsing and serializing JSON, significantly reducing the number of stages and execution time.
Key Points:
- Reduced process complexity by consolidating logic into a custom code stage.
- Improved execution speed by using efficient .NET classes for HTTP and JSON handling.
- Enhanced maintainability and readability of the process.
Example:
using System.Net.Http;
using Newtonsoft.Json;
public async Task<string> FetchDataFromApiAsync(string apiUrl)
{
using (var client = new HttpClient())
{
HttpResponseMessage response = await client.GetAsync(apiUrl);
if (response.IsSuccessStatusCode)
{
string content = await response.Content.ReadAsStringAsync();
return content; // Return the JSON response
}
else
{
// Handle HTTP request errors
return null;
}
}
}
This custom code stage streamlined the process by directly interacting with the API and handling JSON data efficiently, showcasing the power of extending Blue Prism with custom code.
