dotnet-csharp-configuration

Name: dotnet-csharp-configuration
Author: wshaddix

65stars10forks

How to install dotnet-csharp-configuration?

wshaddix/dotnet-skills/dotnet-csharp-configuration

$npx -y skills add wshaddix/dotnet-skills --skill dotnet-csharp-configuration

Installs into the current project.

Summary

Using Options pattern, user secrets, or feature flags. IOptions<T> and FeatureManagement.

Files · 1

View on GitHub

SKILL.md

1	# dotnet-csharp-configuration
2
3	Configuration patterns for .NET applications using Microsoft.Extensions.Configuration and Microsoft.Extensions.Options. Covers the Options pattern (`IOptions<T>`, `IOptionsMonitor<T>`, `IOptionsSnapshot<T>`), validation, user secrets, environment-based configuration, and feature flags with `Microsoft.FeatureManagement`.
4
5	Cross-references: [skill:dotnet-csharp-dependency-injection] for service registration patterns, [skill:dotnet-csharp-coding-standards] for naming conventions.
6
7	---
8
9	## Configuration Sources and Precedence
10
11	Default configuration sources in `WebApplication.CreateBuilder` (last wins):
12
13	1. `appsettings.json`
14	2. `appsettings.{Environment}.json`
15	3. User secrets (Development only)
16	4. Environment variables
17	5. Command-line arguments
18
19	```csharp
20	var builder = WebApplication.CreateBuilder(args);
21	// Sources above are loaded automatically. Add custom sources:
22	builder.Configuration.AddJsonFile("features.json", optional: true, reloadOnChange: true);
23	```
24
25	---
26
27	## Options Pattern
28
29	Bind configuration sections to strongly typed classes and inject them via DI.
30
31	### Defining Options Classes
32
33	```csharp
34	public sealed class SmtpOptions
35	{
36	public const string SectionName = "Smtp";
37
38	public string Host { get; set; } = "";
39	public int Port { get; set; } = 587;
40	public string FromAddress { get; set; } = "";
41	public bool UseSsl { get; set; } = true;
42	}
43	```
44
45	> Options classes use `{ get; set; }` (not `init`) because the configuration binder and `PostConfigure` need to mutate properties. Use `[Required]` via data annotations for mandatory fields instead.
46
47	### Registration
48
49	```csharp
50	builder.Services
51	.AddOptions<SmtpOptions>()
52	.BindConfiguration(SmtpOptions.SectionName)
53	.ValidateDataAnnotations()
54	.ValidateOnStart();
55	```
56
57	### `appsettings.json`
58
59	```json
60	{
61	"Smtp": {
62	"Host": "smtp.example.com",
63	"Port": 587,
64	"FromAddress": "noreply@example.com",
65	"UseSsl": true
66	}
67	}
68	```
69
70	---
71
72	## Options Interfaces
73
74	\| Interface \| Lifetime \| Reload Behavior \| Use Case \|
75	\|-----------\|----------\|-----------------\|----------\|
76	\| `IOptions<T>` \| Singleton \| Never reloads after startup \| Static config, most services \|
77	\| `IOptionsSnapshot<T>` \| Scoped \| Reloads per request/scope \| Per-request config in ASP.NET \|
78	\| `IOptionsMonitor<T>` \| Singleton \| Live reload + change notification \| Singletons, background services \|
79
80	### Injection Examples
81
82	```csharp
83	// Static -- most common, singleton-safe
84	public sealed class EmailService(IOptions<SmtpOptions> options)
85	{
86	private readonly SmtpOptions _smtp = options.Value;
87
88	public Task SendAsync(string to, string subject, string body,
89	CancellationToken ct = default)
90	{
91	// Use _smtp.Host, _smtp.Port, etc.
92	return Task.CompletedTask;
93	}
94	}
95
96	// Live reload in singletons -- monitors config file changes
97	public sealed class FeatureService(IOptionsMonitor<FeatureOptions> monitor)
98	{
99	public bool IsEnabled(string feature)
100	=> monitor.CurrentValue.EnabledFeatures.Contains(feature);
101	}
102
103	// Per-request in scoped services -- reads latest config each request
104	public sealed class PricingService(IOptionsSnapshot<PricingOptions> snapshot)
105	{
106	public decimal GetMarkup() => snapshot.Value.MarkupPercent;
107	}
108	```
109
110	### Change Notifications with `IOptionsMonitor<T>`
111
112	```csharp
113	public sealed class CacheService : IDisposable
114	{
115	private readonly IDisposable? _changeListener;
116	private CacheOptions _current;
117
118	public CacheService(IOptionsMonitor<CacheOptions> monitor)
119	{
120	_current = monitor.CurrentValue;
121	_changeListener = monitor.OnChange(updated =>
122	{
123	_current = updated;
124	// React to config change -- flush cache, resize pool, etc.
125	});
126	}
127
128	public void Dispose() => _changeListener?.Dispose();
129	}
130	```
131
132	---
133
134	## Options Validation
135
136	### Data Annotations
137
138	```csharp
139	using System.ComponentModel.DataAnnotations;
140
141	public sealed class SmtpOptions
142	{
143	public const string SectionName = "Smtp";
144
145	[Required, MinLength(1)]
146	public string Host { get; set; } = "";
147
148	[Range(1, 65535)]
149	public int Port { get; set; } = 587;
150
151	[Required, EmailAddress]
152	public string FromAddress { get; set; } = "";
153	}
154
155	builder.Services
156	.AddOptions<SmtpOptions>()
157	.BindConfiguration(SmtpOptions.SectionName)
158	.ValidateDataAnnotations()
159	.ValidateOnStart(); // Fail fast at startup, not on first use
160	```
161
162	### `IValidateOptions<T>` (Complex Validation)
163
164	Use when validation logic requires cross-property checks or external dependencies.
165
166	```csharp
167	public sealed class SmtpOptionsValidator : IValidateOptions<SmtpOptions>
168	{
169	public ValidateOptionsResult Validate(string? name, SmtpOptions options)
170	{
171	var failures = new List<string>();
172
173	if (options.UseSsl && options.Port == 25)
174	{
175	failures.A

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dotnet-csharp-configuration

65stars10forks

View on GitHub

How to install dotnet-csharp-configuration?

wshaddix/dotnet-skills/dotnet-csharp-configuration

$npx -y skills add wshaddix/dotnet-skills --skill dotnet-csharp-configuration

Installs into the current project.

Summary

Using Options pattern, user secrets, or feature flags. IOptions<T> and FeatureManagement.

Files · 1

View on GitHub

SKILL.md

1	# dotnet-csharp-configuration
2
3	Configuration patterns for .NET applications using Microsoft.Extensions.Configuration and Microsoft.Extensions.Options. Covers the Options pattern (`IOptions<T>`, `IOptionsMonitor<T>`, `IOptionsSnapshot<T>`), validation, user secrets, environment-based configuration, and feature flags with `Microsoft.FeatureManagement`.
4
5	Cross-references: [skill:dotnet-csharp-dependency-injection] for service registration patterns, [skill:dotnet-csharp-coding-standards] for naming conventions.
6
7	---
8
9	## Configuration Sources and Precedence
10
11	Default configuration sources in `WebApplication.CreateBuilder` (last wins):
12
13	1. `appsettings.json`
14	2. `appsettings.{Environment}.json`
15	3. User secrets (Development only)
16	4. Environment variables
17	5. Command-line arguments
18
19	```csharp
20	var builder = WebApplication.CreateBuilder(args);
21	// Sources above are loaded automatically. Add custom sources:
22	builder.Configuration.AddJsonFile("features.json", optional: true, reloadOnChange: true);
23	```
24
25	---
26
27	## Options Pattern
28
29	Bind configuration sections to strongly typed classes and inject them via DI.
30
31	### Defining Options Classes
32
33	```csharp
34	public sealed class SmtpOptions
35	{
36	public const string SectionName = "Smtp";
37
38	public string Host { get; set; } = "";
39	public int Port { get; set; } = 587;
40	public string FromAddress { get; set; } = "";
41	public bool UseSsl { get; set; } = true;
42	}
43	```
44
45	> Options classes use `{ get; set; }` (not `init`) because the configuration binder and `PostConfigure` need to mutate properties. Use `[Required]` via data annotations for mandatory fields instead.
46
47	### Registration
48
49	```csharp
50	builder.Services
51	.AddOptions<SmtpOptions>()
52	.BindConfiguration(SmtpOptions.SectionName)
53	.ValidateDataAnnotations()
54	.ValidateOnStart();
55	```
56
57	### `appsettings.json`
58
59	```json
60	{
61	"Smtp": {
62	"Host": "smtp.example.com",
63	"Port": 587,
64	"FromAddress": "noreply@example.com",
65	"UseSsl": true
66	}
67	}
68	```
69
70	---
71
72	## Options Interfaces
73
74	\| Interface \| Lifetime \| Reload Behavior \| Use Case \|
75	\|-----------\|----------\|-----------------\|----------\|
76	\| `IOptions<T>` \| Singleton \| Never reloads after startup \| Static config, most services \|
77	\| `IOptionsSnapshot<T>` \| Scoped \| Reloads per request/scope \| Per-request config in ASP.NET \|
78	\| `IOptionsMonitor<T>` \| Singleton \| Live reload + change notification \| Singletons, background services \|
79
80	### Injection Examples
81
82	```csharp
83	// Static -- most common, singleton-safe
84	public sealed class EmailService(IOptions<SmtpOptions> options)
85	{
86	private readonly SmtpOptions _smtp = options.Value;
87
88	public Task SendAsync(string to, string subject, string body,
89	CancellationToken ct = default)
90	{
91	// Use _smtp.Host, _smtp.Port, etc.
92	return Task.CompletedTask;
93	}
94	}
95
96	// Live reload in singletons -- monitors config file changes
97	public sealed class FeatureService(IOptionsMonitor<FeatureOptions> monitor)
98	{
99	public bool IsEnabled(string feature)
100	=> monitor.CurrentValue.EnabledFeatures.Contains(feature);
101	}
102
103	// Per-request in scoped services -- reads latest config each request
104	public sealed class PricingService(IOptionsSnapshot<PricingOptions> snapshot)
105	{
106	public decimal GetMarkup() => snapshot.Value.MarkupPercent;
107	}
108	```
109
110	### Change Notifications with `IOptionsMonitor<T>`
111
112	```csharp
113	public sealed class CacheService : IDisposable
114	{
115	private readonly IDisposable? _changeListener;
116	private CacheOptions _current;
117
118	public CacheService(IOptionsMonitor<CacheOptions> monitor)
119	{
120	_current = monitor.CurrentValue;
121	_changeListener = monitor.OnChange(updated =>
122	{
123	_current = updated;
124	// React to config change -- flush cache, resize pool, etc.
125	});
126	}
127
128	public void Dispose() => _changeListener?.Dispose();
129	}
130	```
131
132	---
133
134	## Options Validation
135
136	### Data Annotations
137
138	```csharp
139	using System.ComponentModel.DataAnnotations;
140
141	public sealed class SmtpOptions
142	{
143	public const string SectionName = "Smtp";
144
145	[Required, MinLength(1)]
146	public string Host { get; set; } = "";
147
148	[Range(1, 65535)]
149	public int Port { get; set; } = 587;
150
151	[Required, EmailAddress]
152	public string FromAddress { get; set; } = "";
153	}
154
155	builder.Services
156	.AddOptions<SmtpOptions>()
157	.BindConfiguration(SmtpOptions.SectionName)
158	.ValidateDataAnnotations()
159	.ValidateOnStart(); // Fail fast at startup, not on first use
160	```
161
162	### `IValidateOptions<T>` (Complex Validation)
163
164	Use when validation logic requires cross-property checks or external dependencies.
165
166	```csharp
167	public sealed class SmtpOptionsValidator : IValidateOptions<SmtpOptions>
168	{
169	public ValidateOptionsResult Validate(string? name, SmtpOptions options)
170	{
171	var failures = new List<string>();
172
173	if (options.UseSsl && options.Port == 25)
174	{
175	failures.A

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