TL;DR

Problem: Client making 90,000 CSOM calls/month, 88% were redundant EnsureUser operations for users already on the site.

Solution: Use FieldUserValue.FromUser() optimistically with ExceptionHandlingScope for server-side try-catch logic.

Impact: 75-85% reduction in API calls (90,000 → 10,800-21,600), saving $68-79/month and dramatically reducing throttling risk.

Key Insight: ExceptionHandlingScope doesn’t reduce server requests—it reduces network round trips. The real savings come from smarter business logic that avoids unnecessary EnsureUser calls.

Code Pattern:

var scope = new ExceptionHandlingScope(clientContext);
using (scope.StartScope()) {
    using (scope.StartTry()) {
        listItem["Field"] = FieldUserValue.FromUser("user@company.com"); // Try optimistic
    }
    using (scope.StartCatch()) {
        var user = clientContext.Web.EnsureUser("user@company.com"); // Fallback if needed
        listItem["Field"] = FieldUserValue.FromUser("user@company.com");
    }
}
clientContext.ExecuteQuery(); // One network call handles all the logic

The Service Prioritization in SharePoint Cost Analysis

Recently, I was working with a client to calculate the cost of enabling Service Prioritization in SharePoint on one of their app registrations. The pricing model is straightforward: USD $0.50 per 1,000 Graph calls and USD $1.00 per 1,000 SP REST/CSOM calls.

During the analysis, I discovered something that caught my attention: their solution was making approximately 90,000 calls per month, and 88% of all their CSOM calls were EnsureUser operations.

This was particularly interesting because the users being “ensured” were already associated with the site where the data was being created. It seemed like there should be a more efficient approach - similar to what’s possible with Graph API.

The Problem with User Field Assignment

If you’ve worked with SharePoint user fields, you’re familiar with this common pattern:

// The standard approach
var user = clientContext.Web.EnsureUser("user@company.com");
clientContext.Load(user);
clientContext.ExecuteQuery(); // Network call #1

listItem["AssignedTo"] = new FieldUserValue()
{
    LookupId = user.Id
};
listItem.Update();
clientContext.ExecuteQuery(); // Network call #2

This requires two network calls for each user assignment. Microsoft provides FieldUserValue.FromUser("user@company.com") as an alternative, but it throws an exception if the user isn’t already “known” to the site. This leads to either making two calls to be safe, or handling exceptions with additional calls.

Discovering ExceptionHandlingScope

While researching optimization approaches, I came across a section in Microsoft’s documentation for “Complete basic operations using SharePoint client library code” about ExceptionHandlingScope.

ExceptionHandlingScope allows you to implement try-catch logic that executes on the SharePoint server rather than requiring multiple round trips from your client application. Instead of this painful dance:

1. Try operation → Network call
2. Handle exception → Network call
3. Retry operation → Network call

You get this beautiful symphony:

1. Send try-catch logic to server → Network call
2. Server handles everything internally
3. Get result → You’re done

Here’s the magic in action:

var scope = new ExceptionHandlingScope(clientContext);

using (scope.StartScope())
{
    using (scope.StartTry())
    {
        // Try the optimistic approach first
        listItem["CaseResponsible"] = FieldUserValue.FromUser("user@company.com");
        listItem.Update();
    }
    
    using (scope.StartCatch())
    {
        // If that fails, ensure the user exists
        var user = clientContext.Web.EnsureUser("user@company.com");
        listItem["CaseResponsible"] = FieldUserValue.FromUser("user@company.com");
    }
}

// Execute once - the server handles all the logic
clientContext.ExecuteQuery();

One network call. That’s it.

The server receives your entire try-catch block, attempts the optimistic operation first, and only falls back to EnsureUser if needed. No round trips. No guessing. No waste.

Real-World Impact: Significant Call Reduction

Looking back at the client scenario with ExceptionHandlingScope:

• Before: ~79,200 EnsureUser calls + ~10,800 actual operations = 90,000 total calls
• After: ~10,800-21,600 operations (depending on how many users need ensuring) = substantial reduction

This represents a potential 75-85% reduction in API calls, with corresponding improvements in both performance and Service Prioritization in SharePoint costs.

The Cost Breakdown

Let’s translate this into actual Service Prioritization in SharePoint costs:

Before optimization:

• 90,000 CSOM calls per month
• At USD $1.00 per 1,000 calls
• Monthly cost: $90

After ExceptionHandlingScope optimization:

• Best case: 10,800 calls (if most users are already known) = $10.80/month
• Worst case: 21,600 calls (if many users need ensuring) = $21.60/month
• Monthly savings: $68.40 - $79.20

Annual savings: $820 - $950

These savings become even more significant at scale. For organizations with multiple solutions or higher call volumes, the cost difference can easily reach thousands of dollars annually.

More importantly, the performance improvements—reduced network latency, faster operations, and lower throttling risk—often provide value that far exceeds the direct cost savings.

Throttling: The Hidden Performance Killer

Beyond cost savings, ExceptionHandlingScope provides significant throttling benefits that are often more impactful than the financial savings.

Understanding SharePoint Throttling

SharePoint applies throttling limits to prevent abuse and ensure service stability. When you exceed these limits, you’ll encounter:

• HTTP 429 (Too Many Requests) responses
• Exponential backoff delays (sometimes minutes)
• User experience degradation as operations slow down
• Potential service interruptions during peak usage

The Throttling Math

In our client scenario:

Before ExceptionHandlingScope:

• 90,000 calls per month = ~3,000 calls per day
• During peak hours, this could easily trigger throttling
• Each throttled request requires retry with exponential backoff
• A single throttled operation can delay your entire batch

After ExceptionHandlingScope:

• 10,800-21,600 calls per month = ~360-720 calls per day
• 10x reduction in throttling risk
• Smoother operation during peak business hours
• More predictable performance for end users

Real-World Throttling Impact

Consider a typical business day where multiple users are creating items simultaneously:

• Without optimization: 88% of your throttling budget consumed by redundant EnsureUser calls
• With ExceptionHandlingScope: 88% of your throttling budget available for actual business operations

The beauty of ExceptionHandlingScope is that it doesn’t just reduce the number of calls—it makes your remaining calls more valuable and less likely to be throttled.

Important: ExceptionHandlingScope Is NOT a Magic Bullet

Critical Disclaimer: ExceptionHandlingScope itself does NOT reduce the number of requests to SharePoint. Each operation within the scope still counts as a separate request for throttling purposes.

The reduction in our scenario comes from changing the approach, not from using ExceptionHandlingScope:

What Actually Reduces Calls

• Before: Always calling EnsureUser + setting the field = 2 calls per user
• After: Using FieldUserValue.FromUser() directly, falling back to EnsureUser only when needed

What ExceptionHandlingScope Actually Does

ExceptionHandlingScope reduces network round trips, not server requests:

• Network benefit: 1 round trip instead of potentially 2-3
• Throttling impact: Each operation still counts toward throttling limits
• Performance gain: Reduced latency, not reduced server load

The Real Magic

The 75-85% reduction in our client scenario comes from this logic change:

// This approach reduces actual requests
// Most users are already known to the site
// So most operations only need 1 request instead of 2
using (scope.StartTry())
{
    // This succeeds for ~80% of users (1 request)
    listItem["Field"] = FieldUserValue.FromUser("user@company.com");
}
using (scope.StartCatch())
{
    // This only runs for ~20% of users (1 request)
    var user = clientContext.Web.EnsureUser("user@company.com");
    listItem["Field"] = FieldUserValue.FromUser("user@company.com");
}

ExceptionHandlingScope simply makes this pattern efficient by handling the try-catch logic server-side instead of requiring multiple network round trips to determine which approach to use.

Bottom line: ExceptionHandlingScope optimizes network efficiency, but the request reduction comes from smarter business logic, not from the scope itself.

The Broader Lesson

This experience highlighted an important principle: before optimizing an existing approach, it’s worth questioning whether there’s a fundamentally different way to solve the problem. In this case, server-side exception handling provided a cleaner solution than client-side optimization or caching strategies.

ExceptionHandlingScope has been available since SharePoint 2013, but it’s not widely discussed in the SharePoint development community. It’s a good reminder to periodically review Microsoft’s documentation for features that might address current challenges in new ways.

Your Next Steps

Before you write your next SharePoint operation that involves potential exceptions:

1. Pause and calculate: How many network calls will your approach generate?
2. Question the pattern: Could server-side logic handle the complexity?
3. Explore ExceptionHandlingScope: Can your try-catch logic run on the server?
4. Measure the impact: Compare network calls before and after implementation

Sometimes the most powerful optimizations come from using the tools that were there all along. ExceptionHandlingScope isn’t just a performance optimization—it’s a reminder that the platform often provides solutions we didn’t know we were looking for.

Next time you’re facing a SharePoint performance challenge, remember: the answer might not be in the latest framework or cutting-edge technique. Sometimes, it’s hiding in plain sight in the documentation you scrolled past.

Jeppe Spanggaard

A passionate software developer. I love to build software that makes a difference!