---
title: Construct InvalidDataException from validation failures
summary: Build an InvalidDataException whose message and ValidationErrors list are derived from a set of validation failures.
status: draft
owner: andmil
last_reviewed: 2026-09-15
library: SAIF.Web.API.Core
reference_type: package
operation_id: OP-CORE-002
trigger: InvalidDataException(IEnumerable<ValidationFailure> failures) constructor invoked by a consumer
---

# Construct InvalidDataException from validation failures

This constructor is the one exception-hierarchy member with conditional/multi-step logic worth documenting as an operation in its own right: it builds an `InvalidDataException` whose `Message` is the semicolon-joined set of the supplied failures' `ErrorMessage` values, and whose `ValidationErrors` list holds all supplied failures ([BR-CORE-001](../business-rules.md#br-core-001-invaliddataexception-validation-failure-projection)).

| Field | Value |
| --- | --- |
| **Operation ID** | OP-CORE-002 |
| **Trigger** | A consumer constructs `InvalidDataException` with a collection of `ValidationFailure` objects |
| **Inputs** | `IEnumerable<ValidationFailure> failures` |
| **Outputs** | A constructed `InvalidDataException` with `Message` and `ValidationErrors` populated |
| **Primary components** | `SAIF.API.Exceptions.InvalidDataException(IEnumerable<ValidationFailure>)` |
| **Entry point** | `src/SAIF.Web.API.Core/SAIFException.cs` |

## Steps

1. Project `failures` to their `ErrorMessage` strings via LINQ `.Select(x => x.ErrorMessage)`. No business rule; no SQL.
2. Join the projected messages using the `ToStringAll(";")` extension method (a member of `SAIF.Common.Extensions`, supplied by a referenced assembly rather than by this project, and presumed to originate from the internal-organization `SAIF.Framework.Common` NuGet package**) and pass the joined string to the base `Exception(string message)` constructor ([BR-CORE-001](../business-rules.md#br-core-001-invaliddataexception-validation-failure-projection)).
   - The join implementation itself was not traced beyond its call site — its defining assembly was not accessible to local source analysis and was not independently retrieved via the Legends CLI RAG service in this pass**.
3. Materialize `failures` to a `List<ValidationFailure>` and assign it to `ValidationErrors` ([BR-CORE-001](../business-rules.md#br-core-001-invaliddataexception-validation-failure-projection)).

## Process flow

The following diagram visualizes this operation's control flow.

```mermaid
flowchart TD
	Start(["InvalidDataException<br>constructed with<br>failures"]) --> Project["Project failures to<br>ErrorMessage strings"]
	Project --> Join["Join messages via<br>ToStringAll<br>semicolon-delimited"]
	Join --> Base["Pass joined string to<br>base Exception<br>constructor"]
	Base --> Assign["Materialize failures to<br>list, assign to<br>ValidationErrors"]
	Assign --> Done([Exception constructed])
```

## Failure and edge-case behavior
- For an empty `failures` collection, the constructor still projects the (empty) sequence and passes it to `ToStringAll(";")`; the resulting message is unknown, since the `ToStringAll` implementation was not traced or independently retrieved**.
- The `ToStringAll` join implementation itself was not traced, since `SAIF.Common.Extensions` is defined outside this repository's scanned source.

## Related documentation
- [Operations and processes](../operations-processes.md)
- [Business rules](../business-rules.md)

> **Note:** Statements marked with `**` could not be confirmed; treat as unknown until verified.

## Sources
- `src/SAIF.Web.API.Core/SAIFException.cs`