> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/App-vNext/Polly/llms.txt
> Use this file to discover all available pages before exploring further.

# Polly.Core

> Core classes and interfaces for the Polly resilience library

## Overview

The Polly.Core namespace provides the foundational types for building and executing resilience pipelines in .NET applications.

## Key Classes

### ResilienceContext

A context assigned to a single execution of a `ResiliencePipeline`. It is created manually or automatically when executing resilience operations.

<ParamField path="OperationKey" type="string?">
  A key unique to the call site of the current execution. This value should have low cardinality (do not use GUIDs).
</ParamField>

<ParamField path="CancellationToken" type="CancellationToken">
  The cancellation token associated with the execution.
</ParamField>

<ParamField path="ContinueOnCapturedContext" type="bool">
  Indicates whether the execution should continue on the captured context.
</ParamField>

<ParamField path="Properties" type="ResilienceProperties">
  Custom properties attached to the context.
</ParamField>

<Warning>
  Do not re-use an instance of `ResilienceContext` across more than one execution. Retrieve contexts from the pool using `ResilienceContextPool.Get(CancellationToken)` and return them with `ResilienceContextPool.Return(ResilienceContext)`.
</Warning>

### Outcome\<TResult>

Represents the outcome of an operation, which can be either a result value or an exception. Used in advanced, low-allocation scenarios.

#### Static Factory Methods

<ResponseField name="FromResult<TResult>" type="Outcome<TResult>">
  Creates an outcome with the given result value.

  <Expandable title="Parameters">
    <ParamField path="value" type="TResult?">
      The result value.
    </ParamField>
  </Expandable>
</ResponseField>

<ResponseField name="FromException<TResult>" type="Outcome<TResult>">
  Creates an outcome with the given exception.

  <Expandable title="Parameters">
    <ParamField path="exception" type="Exception" required>
      The exception that occurred.
    </ParamField>
  </Expandable>
</ResponseField>

<ResponseField name="FromResultAsValueTask<TResult>" type="ValueTask<Outcome<TResult>>">
  Returns an outcome with the given value wrapped as a completed `ValueTask`.

  <Expandable title="Parameters">
    <ParamField path="value" type="TResult">
      The result value.
    </ParamField>
  </Expandable>
</ResponseField>

<ResponseField name="FromExceptionAsValueTask<TResult>" type="ValueTask<Outcome<TResult>>">
  Returns an outcome with the given exception wrapped as a completed `ValueTask`.

  <Expandable title="Parameters">
    <ParamField path="exception" type="Exception" required>
      The exception that occurred.
    </ParamField>
  </Expandable>
</ResponseField>

## Example Usage

```csharp theme={null}
using Polly;

// Create a context from the pool
var context = ResilienceContextPool.Shared.Get(cancellationToken);
context.OperationKey = "my-operation";

try
{
    // Use the context in pipeline execution
    await pipeline.ExecuteAsync(
        static (ctx, state) => { /* your logic */ },
        context,
        state);
}
finally
{
    // Always return the context to the pool
    ResilienceContextPool.Shared.Return(context);
}
```

```csharp theme={null}
// Using Outcome for advanced scenarios
public async ValueTask<Outcome<string>> GetDataAsync(
    ResilienceContext context,
    CancellationToken ct)
{
    try
    {
        var result = await FetchDataAsync(ct);
        return Outcome.FromResult(result);
    }
    catch (Exception ex)
    {
        return Outcome.FromException<string>(ex);
    }
}
```