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Can't access arguments of attribute from system library using source generator

I am trying to make a source generator for mapping columns from the google bigquery api client to class properties. I'm having trouble getting custom column names from a ColumnAttribute on the properties. ConstructorArguments is always empty and columnAttribute.AttributeClass in this sample is always an ErrorTypeSymbol. If I try to load that type using compilation.GetTypeByMetadataName("System.ComponentModel.DataAnnotations.Schema.ColumnAttribute") the result is always null.
using System.Collections.Immutable;
using System.Diagnostics;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Text;
namespace BigQueryMapping;
[Generator]
public class BigQueryMapperGenerator : IIncrementalGenerator
{
public void Initialize(IncrementalGeneratorInitializationContext context)
{
// add marker attribute
context.RegisterPostInitializationOutput(ctx =>
ctx.AddSource("BigQueryMappedAttribute.g.cs", SourceText.From(Attribute, Encoding.UTF8)));
// add static interface
context.RegisterPostInitializationOutput(ctx =>
ctx.AddSource("BigQueryMappedInterface.g.cs", SourceText.From(Interface, Encoding.UTF8)));
// get classes
IncrementalValuesProvider<ClassDeclarationSyntax> classDeclarations = context.SyntaxProvider
.CreateSyntaxProvider(
predicate: static (s, _) => s is ClassDeclarationSyntax c && c.AttributeLists.Any(),
transform: static (ctx, _) => GetSemanticTargetForGeneration(ctx)
)
.Where(static m => m is not null)!;
IncrementalValueProvider<(Compilation Compilation, ImmutableArray<ClassDeclarationSyntax>Syntaxes)>
compilationAndClasses = context.CompilationProvider.Combine(classDeclarations.Collect());
context.RegisterSourceOutput(compilationAndClasses,
static (spc, source) => Execute(source.Compilation, source.Syntaxes, spc));
static ClassDeclarationSyntax? GetSemanticTargetForGeneration(GeneratorSyntaxContext context)
{
var classDeclarationSyntax = (ClassDeclarationSyntax)context.Node;
foreach (var attributeListSyntax in classDeclarationSyntax.AttributeLists)
{
foreach (var attributeSyntax in attributeListSyntax.Attributes)
{
var fullName = context.SemanticModel.GetTypeInfo(attributeSyntax).Type?.ToDisplayString();
if (fullName == "BigQueryMapping.BigQueryMappedAttribute")
return classDeclarationSyntax;
}
}
return null;
}
static void Execute(Compilation compilation, ImmutableArray<ClassDeclarationSyntax> classes,
SourceProductionContext context)
{
try
{
if (classes.IsDefaultOrEmpty)
return;
var distinctClasses = classes.Distinct();
var classesToGenerate = GetTypesToGenerate(compilation, distinctClasses, context.CancellationToken);
foreach (var classToGenerate in classesToGenerate)
{
var result = GeneratePartialClass(classToGenerate);
context.AddSource($"{classToGenerate.RowClass.Name}.g.cs", SourceText.From(result, Encoding.UTF8));
}
}
catch (Exception e)
{
var descriptor = new DiagnosticDescriptor(id: "BQD001",
title: "Error creating bigquery mapper",
messageFormat: "{0} {1}",
category: "BigQueryMapperGenerator",
DiagnosticSeverity.Error,
isEnabledByDefault: true);
context.ReportDiagnostic(Diagnostic.Create(descriptor, null, e.Message, e.StackTrace));
}
}
}
static IEnumerable<ClassToGenerate> GetTypesToGenerate(Compilation compilation,
IEnumerable<ClassDeclarationSyntax> classes,
CancellationToken ct)
{
var columnAttributeSymbol =
compilation.GetTypeByMetadataName("System.ComponentModel.DataAnnotations.Schema.ColumnAttribute");
foreach (var #class in classes)
{
Debug.WriteLine($"Checking class {#class}");
ct.ThrowIfCancellationRequested();
var semanticModel = compilation.GetSemanticModel(#class.SyntaxTree);
if (semanticModel.GetDeclaredSymbol(#class) is not INamedTypeSymbol classSymbol)
continue;
var info = new ClassToGenerate(classSymbol, new());
foreach (var member in classSymbol.GetMembers())
{
if (member is IPropertySymbol propertySymbol)
{
if (propertySymbol.DeclaredAccessibility == Accessibility.Public)
{
if (propertySymbol.SetMethod is not null)
{
var columnName = propertySymbol.Name;
var columnAttribute = propertySymbol.GetAttributes().FirstOrDefault(a =>
a.AttributeClass!.ToDisplayString() == "Column");
if (columnAttribute is not null)
{
if (!columnAttribute.ConstructorArguments.IsDefaultOrEmpty)
{
var nameArg = columnAttribute.ConstructorArguments.First();
if (nameArg.Value is string name)
{
columnName = name;
}
}
}
info.Properties.Add((columnName, propertySymbol));
}
}
}
}
yield return info;
}
}
static string GeneratePartialClass(ClassToGenerate c)
{
var sb = new StringBuilder();
sb.Append($#"// <auto-generated/>
namespace {c.RowClass.ContainingNamespace.ToDisplayString()}
{{
public partial class {c.RowClass.Name} : BigQueryMapping.IBigQueryGenerated<{c.RowClass.Name}>
{{
public static {c.RowClass.Name} FromBigQueryRow(Google.Cloud.BigQuery.V2.BigQueryRow row)
{{
return new {c.RowClass.Name}
{{");
foreach (var (columnName, property) in c.Properties)
{
// would like to check if key exists but don't see any sort of ContainsKey implemented on BigQueryRow
var tempName = $"___{property.Name}";
var basePropertyType = property.Type.WithNullableAnnotation(NullableAnnotation.None).ToDisplayString();
if (basePropertyType.EndsWith("?"))
{
basePropertyType = basePropertyType.Substring(default, basePropertyType.Length - 1);
}
sb.Append($#"
{property.Name} = row[""{columnName}""] is {basePropertyType} {tempName} ? {tempName} : default,");
}
sb.Append($#"
}};
}}
}}
}}");
return sb.ToString();
}
private record struct ClassToGenerate(INamedTypeSymbol RowClass,
List<(string ColumnName, IPropertySymbol Property)> Properties);
public const string Attribute = /* lang=csharp */ #"// <auto-generated/>
namespace BigQueryMapping {
[System.AttributeUsage(System.AttributeTargets.Class)]
public class BigQueryMappedAttribute : System.Attribute
{
}
}";
public const string Interface = /* lang=csharp */ #"// <auto-generated/>
namespace BigQueryMapping {
public interface IBigQueryGenerated<TRow> {
static TRow FromBigQueryRow(Google.Cloud.BigQuery.V2.BigQueryRow row) => throw new System.NotImplementedException();
}
}";
}
I have tried this with both System.ComponentModel.DataAnnotations.Schema.ColumnAttribute and a custom attribute injected via context.RegisterPostInitializationOutput to similar results. I have also tried rewriting this to use ISourceGenerator instead of IIncrementalGenerator and gotten the same behavior. Am wondering what I need to do to get columnAttribute loading correctly.
Thanks for any help in advance

It's hard to psychic debug the code but this does jump out:
var columnAttribute = propertySymbol.GetAttributes().FirstOrDefault(a =>
a.AttributeClass!.ToDisplayString() == "Column");
I'd guess the class here would be the fully qualified name. You already fetched the ColumnAttribute type earlier, so what'd be even better is to compare the AttributeClass to that type rather than doing string checks like this.
As a semi-related comment, if you're looking for types/members that are annotated with a specific attribute, rather than doing it yourself we have SyntaxValueProvider.ForAttributeWithMetadataName which is pretty heavily optimized to reduce the performance impact on your Visual Studio. It requires 17.3 or higher, but as long as you're OK with that it'll generally help performance.

Roslyn - get grouped single line comments

I am writing a program in C# for extracting comments from code. I am using Roslyn compiler to do that. It's great, because I am just visiting the whole abstract syntax tree and fetching SingleLineComment trivia, MultiLineComment trivia and DocumentationComment trivia syntax from the file in solution. But there is a problem because programmers often write comments like that:
// General Information about an assembly is controlled through the following
// set of attributes. Change these attribute values to modify the information
// associated with an assembly.
You can see that these are three single line comments, but I want them them to be fetched from code as one comment. Can I achieve that with Roslyn or maybe there is another way? Because that's frequent situation when programmers are writing multi line commments using single line comments syntax.
My code for extracting comments looks like this:
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using System.Collections.Generic;
namespace RoslynPlay
{
public class CommentStore
{
public List<Comment> Comments { get; } = new List<Comment>();
public void AddCommentTrivia(SyntaxTrivia trivia,
LocationStore commentLocationstore, string fileName)
{
if (trivia.Kind() == SyntaxKind.SingleLineCommentTrivia)
{
Comments.Add(new SingleLineComment(trivia.ToString(),
trivia.GetLocation().GetLineSpan().EndLinePosition.Line + 1, commentLocationstore)
{
FileName = fileName,
});
}
else if (trivia.Kind() == SyntaxKind.MultiLineCommentTrivia)
{
Comments.Add(new MultiLineComment(trivia.ToString(),
trivia.GetLocation().GetLineSpan().StartLinePosition.Line + 1,
trivia.GetLocation().GetLineSpan().EndLinePosition.Line + 1, commentLocationstore)
{
FileName = fileName,
});
}
}
public void AddCommentNode(DocumentationCommentTriviaSyntax node,
LocationStore commentLocationstore, string fileName)
{
Comments.Add(new DocComment(node.ToString(),
node.GetLocation().GetLineSpan().StartLinePosition.Line + 1,
node.GetLocation().GetLineSpan().EndLinePosition.Line,
commentLocationstore)
{
FileName = fileName,
});
}
}
}
and in main main file (Program.cs) I am launching comment extraction from code like this:
string fileContent;
SyntaxTree tree;
SyntaxNode root;
CommentsWalker commentWalker;
MethodsAndClassesWalker methodWalker;
string[] files = Directory.GetFiles(projectPath, $"*.cs", SearchOption.AllDirectories);
var commentStore = new CommentStore();
Console.WriteLine("Reading files...");
ProgressBar progressBar = new ProgressBar(files.Length);
foreach (var file in files)
{
fileContent = File.ReadAllText(file);
string filePath = new Regex($#"{projectPath}\\(.*)$").Match(file).Groups[1].ToString();
tree = CSharpSyntaxTree.ParseText(fileContent);
root = tree.GetRoot();
commentWalker = new CommentsWalker(filePath, commentStore);
commentWalker.Visit(root);
progressBar.UpdateAndDisplay();
}
and here is also the comment walker:
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
namespace RoslynPlay
{
public class CommentsWalker : CSharpSyntaxWalker
{
private string _fileName;
private CommentStore _commentStore;
public CommentsWalker(string fileName,
CommentStore commentStore)
: base(SyntaxWalkerDepth.StructuredTrivia)
{
_fileName = fileName;
_commentStore = commentStore;
}
public override void VisitTrivia(SyntaxTrivia trivia)
{
if (trivia.Kind() == SyntaxKind.SingleLineCommentTrivia
|| trivia.Kind() == SyntaxKind.MultiLineCommentTrivia)
{
_commentStore.AddCommentTrivia(trivia, _commentLocationStore, _fileName);
}
base.VisitTrivia(trivia);
}
public override void VisitDocumentationCommentTrivia(DocumentationCommentTriviaSyntax node)
{
_commentStore.AddCommentNode(node, _commentLocationStore, _fileName);
base.VisitDocumentationCommentTrivia(node);
}
}
}
And the problem is because trivia.Kind() == SyntaxKind.SingleLineCommentTrivia extracts only single line of comments, but I want to extract single line comments blocks as one comment.

Change files using Roslyn

I'm trying to write a command line tool that modifies some code using Roslyn. Everything seems to go well: the solution is opened, the solution is changed, the Workspace.TryApplyChanges method returns true. However no actual files are changed on disk. What's up? Below is the top level code I'm using.
static void Main(string[] args)
{
var solutionPath = args[0];
UpdateAnnotations(solutionPath).Wait();
}
static async Task<bool> UpdateAnnotations(string solutionPath)
{
using (var workspace = MSBuildWorkspace.Create())
{
var solution = await workspace.OpenSolutionAsync(solutionPath);
var newSolution = await SolutionAttributeUpdater.UpdateAttributes(solution);
var result = workspace.TryApplyChanges(newSolution);
Console.WriteLine(result);
return result;
}
}

I constructed a short program using your code and received the results I expected - the problem appears to reside within the SolutionAttributeUpdater.UpdateAttributes method. I received these results using the following implementation with your base main and UpdateAnnotations-methods:
public class SolutionAttributeUpdater
{
public static async Task<Solution> UpdateAttributes(Solution solution)
{
foreach (var project in solution.Projects)
{
foreach (var document in project.Documents)
{
var syntaxTree = await document.GetSyntaxTreeAsync();
var root = syntaxTree.GetRoot();
var descentants = root.DescendantNodes().Where(curr => curr is AttributeListSyntax).ToList();
if (descentants.Any())
{
var attributeList = SyntaxFactory.AttributeList(
SyntaxFactory.SingletonSeparatedList(
SyntaxFactory.Attribute(SyntaxFactory.IdentifierName("Cookies"), SyntaxFactory.AttributeArgumentList(SyntaxFactory.SeparatedList(new[] { SyntaxFactory.AttributeArgument(
SyntaxFactory.LiteralExpression(
SyntaxKind.StringLiteralExpression, SyntaxFactory.Literal(#"Sample"))
)})))));
root = root.ReplaceNodes(descentants, (node, n2) => attributeList);
solution = solution.WithDocumentSyntaxRoot(document.Id, root);
}
}
}
return solution;
}
}
It was tested using the following class in the sample solution:
public class SampleClass<T>
{
[DataMember("Id")]
public int Property { get; set; }
[DataMember("Id")]
public void DoStuff()
{
DoStuff();
}
}
And it resulted in the following Output:
public class SampleClass<T>
{
[Cookies("Sample")] public int Property { get; set; }
[Cookies("Sample")] public void DoStuff()
{
DoStuff();
}
}
If you take a look at the UpdateAttributes method I had to replace the nodes with ReplaceNodes and updated the solution by calling WithDocumentSyntaxRoot.
I would assume that either one of those two calls is missing or that nothing was changed at all - if you call workspace.TryApplyChanges(solution) you would still receive true as an Output.
Note that using multiple calls of root.ReplaceNode() instead of root.ReplaceNodes() can also result in an error since only the first update is actually used for the modified document - which might lead you to believe that nothing has changed at all, depending on the implementation.

HtmlAgilityPack XPath case ignoring

When I use
SelectSingleNode("//meta[#name='keywords']")
it doesn't work, but when I use the same case that used in original document it works good:
SelectSingleNode("//meta[#name='Keywords']")
So the question is how can I set case ignoring?

If the actual value is an unknown case, I think you have to use translate. I believe it's:
SelectSingleNode("//meta[translate(#name,'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz')='keywords']")
This is the hack, but it's the only option in XPath 1.0 (except the opposite to upper-case).

If you need a more comprehensive solution, you can write an extension function for the XPath processor which will perform a case insensitive comparison. It is quite a bit of code, but you only write it once.
After implementing the extension you can write your query as follows
"//meta[#name[Extensions:CaseInsensitiveComparison('Keywords')]]"
Where Extensions:CaseInsensitiveComparison is the extension function implemented in the sample below.
NOTE: this is not well tested I just threw it together for this response so the error handling etc. is non-existent!
The following is the code for the custom XSLT Context which provides one or more extension functions
using System;
using System.Xml.XPath;
using System.Xml.Xsl;
using System.Xml;
using HtmlAgilityPack;
public class XsltCustomContext : XsltContext
{
public const string NamespaceUri = "http://XsltCustomContext";
public XsltCustomContext()
{
}
public XsltCustomContext(NameTable nt)
: base(nt)
{
}
public override IXsltContextFunction ResolveFunction(string prefix, string name, XPathResultType[] ArgTypes)
{
// Check that the function prefix is for the correct namespace
if (this.LookupNamespace(prefix) == NamespaceUri)
{
// Lookup the function and return the appropriate IXsltContextFunction implementation
switch (name)
{
case "CaseInsensitiveComparison":
return CaseInsensitiveComparison.Instance;
}
}
return null;
}
public override IXsltContextVariable ResolveVariable(string prefix, string name)
{
return null;
}
public override int CompareDocument(string baseUri, string nextbaseUri)
{
return 0;
}
public override bool PreserveWhitespace(XPathNavigator node)
{
return false;
}
public override bool Whitespace
{
get { return true; }
}
// Class implementing the XSLT Function for Case Insensitive Comparison
class CaseInsensitiveComparison : IXsltContextFunction
{
private static XPathResultType[] _argTypes = new XPathResultType[] { XPathResultType.String };
private static CaseInsensitiveComparison _instance = new CaseInsensitiveComparison();
public static CaseInsensitiveComparison Instance
{
get { return _instance; }
}
#region IXsltContextFunction Members
public XPathResultType[] ArgTypes
{
get { return _argTypes; }
}
public int Maxargs
{
get { return 1; }
}
public int Minargs
{
get { return 1; }
}
public XPathResultType ReturnType
{
get { return XPathResultType.Boolean; }
}
public object Invoke(XsltContext xsltContext, object[] args, XPathNavigator navigator)
{
// Perform the function of comparing the current element to the string argument
// NOTE: You should add some error checking here.
string text = args[0] as string;
return string.Equals(navigator.Value, text, StringComparison.InvariantCultureIgnoreCase);
}
#endregion
}
}
You can then use the above extension function in your XPath queries, here is an example for our case
class Program
{
static string html = "<html><meta name=\"keywords\" content=\"HTML, CSS, XML\" /></html>";
static void Main(string[] args)
{
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(html);
XPathNavigator nav = doc.CreateNavigator();
// Create the custom context and add the namespace to the context
XsltCustomContext ctx = new XsltCustomContext(new NameTable());
ctx.AddNamespace("Extensions", XsltCustomContext.NamespaceUri);
// Build the XPath query using the new function
XPathExpression xpath =
XPathExpression.Compile("//meta[#name[Extensions:CaseInsensitiveComparison('Keywords')]]");
// Set the context for the XPath expression to the custom context containing the
// extensions
xpath.SetContext(ctx);
var element = nav.SelectSingleNode(xpath);
// Now we have the element
}
}

This is how I do it:
HtmlNodeCollection MetaDescription = document.DocumentNode.SelectNodes("//meta[#name='description' or #name='Description' or #name='DESCRIPTION']");
string metaDescription = MetaDescription != null ? HttpUtility.HtmlDecode(MetaDescription.FirstOrDefault().Attributes["content"].Value) : string.Empty;

Alternatively use the new Linq syntax which should support case insensitive matching:
node = doc.DocumentNode.Descendants("meta")
.Where(meta => meta.Attributes["name"] != null)
.Where(meta => string.Equals(meta.Attributes["name"].Value, "keywords", StringComparison.OrdinalIgnoreCase))
.Single();
But you have to do an ugly null check for the attributes in order to prevent a NullReferenceException...

How do you upgrade Settings.settings when the stored data type changes?

I have an application that stores a collection of objects in the user settings, and is deployed via ClickOnce. The next version of the applications has a modified type for the objects stored. For example, the previous version's type was:
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
}
And the new version's type is:
public class Person
{
public string Name { get; set; }
public DateTime DateOfBirth { get; set; }
}
Obviously, ApplicationSettingsBase.Upgrade wouldn't know how to perform an upgrade, since Age needs to be converted using (age) => DateTime.Now.AddYears(-age), so only the Name property would be upgraded, and DateOfBirth would just have the value of Default(DateTime).
So I'd like to provide an upgrade routine, by overriding ApplicationSettingsBase.Upgrade, that would convert the values as needed. But I've ran into three problems:
When trying to access the previous version's value using ApplicationSettingsBase.GetPreviousVersion, the returned value would be an object of the current version, which doesn't have the Age property and has an empty DateOfBirth property (since it can't deserialize Age into DateOfBirth).
I couldn't find a way to find out from which version of the application I'm upgrading. If there is an upgrade procedure from v1 to v2 and a procedure from v2 to v3, if a user is upgrading from v1 to v3, I need to run both upgrade procedures in order, but if the user is upgrading from v2, I only need to run the second upgrade procedure.
Even if I knew what the previous version of the application is, and I could access the user settings in their former structure (say by just getting a raw XML node), if I wanted to chain upgrade procedures (as described in issue 2), where would I store the intermediate values? If upgrading from v2 to v3, the upgrade procedure would read the old values from v2 and write them directly to the strongly-typed settings wrapper class in v3. But if upgrading from v1, where would I put the results of the v1 to v2 upgrade procedure, since the application only has a wrapper class for v3?
I thought I could avoid all these issues if the upgrade code would perform the conversion directly on the user.config file, but I found no easy way to get the location of the user.config of the previous version, since LocalFileSettingsProvider.GetPreviousConfigFileName(bool) is a private method.
Does anyone have a ClickOnce-compatible solution for upgrading user settings that change type between application versions, preferably a solution that can support skipping versions (e.g. upgrading from v1 to v3 without requiring the user to in install v2)?

I ended up using a more complex way to do upgrades, by reading the raw XML from the user settings file, then run a series of upgrade routines that refactor the data to the way it's supposed to be in the new next version. Also, due to a bug I found in ClickOnce's ApplicationDeployment.CurrentDeployment.IsFirstRun property (you can see the Microsoft Connect feedback here), I had to use my own IsFirstRun setting to know when to perform the upgrade. The whole system works very well for me (but it was made with blood and sweat due to a few very stubborn snags). Ignore comments mark what is specific to my application and is not part of the upgrade system.
using System;
using System.Collections.Specialized;
using System.Configuration;
using System.Xml;
using System.IO;
using System.Linq;
using System.Windows.Forms;
using System.Reflection;
using System.Text;
using MyApp.Forms;
using MyApp.Entities;
namespace MyApp.Properties
{
public sealed partial class Settings
{
private static readonly Version CurrentVersion = Assembly.GetExecutingAssembly().GetName().Version;
private Settings()
{
InitCollections(); // ignore
}
public override void Upgrade()
{
UpgradeFromPreviousVersion();
BadDataFiles = new StringCollection(); // ignore
UpgradePerformed = true; // this is a boolean value in the settings file that is initialized to false to indicate that settings file is brand new and requires upgrading
InitCollections(); // ignore
Save();
}
// ignore
private void InitCollections()
{
if (BadDataFiles == null)
BadDataFiles = new StringCollection();
if (UploadedGames == null)
UploadedGames = new StringDictionary();
if (SavedSearches == null)
SavedSearches = SavedSearchesCollection.Default;
}
private void UpgradeFromPreviousVersion()
{
try
{
// This works for both ClickOnce and non-ClickOnce applications, whereas
// ApplicationDeployment.CurrentDeployment.DataDirectory only works for ClickOnce applications
DirectoryInfo currentSettingsDir = new FileInfo(ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal).FilePath).Directory;
if (currentSettingsDir == null)
throw new Exception("Failed to determine the location of the settings file.");
if (!currentSettingsDir.Exists)
currentSettingsDir.Create();
// LINQ to Objects for .NET 2.0 courtesy of LINQBridge (linqbridge.googlecode.com)
var previousSettings = (from dir in currentSettingsDir.Parent.GetDirectories()
let dirVer = new { Dir = dir, Ver = new Version(dir.Name) }
where dirVer.Ver < CurrentVersion
orderby dirVer.Ver descending
select dirVer).FirstOrDefault();
if (previousSettings == null)
return;
XmlElement userSettings = ReadUserSettings(previousSettings.Dir.GetFiles("user.config").Single().FullName);
userSettings = SettingsUpgrader.Upgrade(userSettings, previousSettings.Ver);
WriteUserSettings(userSettings, currentSettingsDir.FullName + #"\user.config", true);
Reload();
}
catch (Exception ex)
{
MessageBoxes.Alert(MessageBoxIcon.Error, "There was an error upgrading the the user settings from the previous version. The user settings will be reset.\n\n" + ex.Message);
Default.Reset();
}
}
private static XmlElement ReadUserSettings(string configFile)
{
// PreserveWhitespace required for unencrypted files due to https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=352591
var doc = new XmlDocument { PreserveWhitespace = true };
doc.Load(configFile);
XmlNode settingsNode = doc.SelectSingleNode("configuration/userSettings/MyApp.Properties.Settings");
XmlNode encryptedDataNode = settingsNode["EncryptedData"];
if (encryptedDataNode != null)
{
var provider = new RsaProtectedConfigurationProvider();
provider.Initialize("userSettings", new NameValueCollection());
return (XmlElement)provider.Decrypt(encryptedDataNode);
}
else
{
return (XmlElement)settingsNode;
}
}
private static void WriteUserSettings(XmlElement settingsNode, string configFile, bool encrypt)
{
XmlDocument doc;
XmlNode MyAppSettings;
if (encrypt)
{
var provider = new RsaProtectedConfigurationProvider();
provider.Initialize("userSettings", new NameValueCollection());
XmlNode encryptedSettings = provider.Encrypt(settingsNode);
doc = encryptedSettings.OwnerDocument;
MyAppSettings = doc.CreateElement("MyApp.Properties.Settings").AppendNewAttribute("configProtectionProvider", provider.GetType().Name);
MyAppSettings.AppendChild(encryptedSettings);
}
else
{
doc = settingsNode.OwnerDocument;
MyAppSettings = settingsNode;
}
doc.RemoveAll();
doc.AppendNewElement("configuration")
.AppendNewElement("userSettings")
.AppendChild(MyAppSettings);
using (var writer = new XmlTextWriter(configFile, Encoding.UTF8) { Formatting = Formatting.Indented, Indentation = 4 })
doc.Save(writer);
}
private static class SettingsUpgrader
{
private static readonly Version MinimumVersion = new Version(0, 2, 1, 0);
public static XmlElement Upgrade(XmlElement userSettings, Version oldSettingsVersion)
{
if (oldSettingsVersion < MinimumVersion)
throw new Exception("The minimum required version for upgrade is " + MinimumVersion);
var upgradeMethods = from method in typeof(SettingsUpgrader).GetMethods(BindingFlags.Static | BindingFlags.NonPublic)
where method.Name.StartsWith("UpgradeFrom_")
let methodVer = new { Version = new Version(method.Name.Substring(12).Replace('_', '.')), Method = method }
where methodVer.Version >= oldSettingsVersion && methodVer.Version < CurrentVersion
orderby methodVer.Version ascending
select methodVer;
foreach (var methodVer in upgradeMethods)
{
try
{
methodVer.Method.Invoke(null, new object[] { userSettings });
}
catch (TargetInvocationException ex)
{
throw new Exception(string.Format("Failed to upgrade user setting from version {0}: {1}",
methodVer.Version, ex.InnerException.Message), ex.InnerException);
}
}
return userSettings;
}
private static void UpgradeFrom_0_2_1_0(XmlElement userSettings)
{
// ignore method body - put your own upgrade code here
var savedSearches = userSettings.SelectNodes("//SavedSearch");
foreach (XmlElement savedSearch in savedSearches)
{
string xml = savedSearch.InnerXml;
xml = xml.Replace("IRuleOfGame", "RuleOfGame");
xml = xml.Replace("Field>", "FieldName>");
xml = xml.Replace("Type>", "Comparison>");
savedSearch.InnerXml = xml;
if (savedSearch["Name"].GetTextValue() == "Tournament")
savedSearch.AppendNewElement("ShowTournamentColumn", "true");
else
savedSearch.AppendNewElement("ShowTournamentColumn", "false");
}
}
}
}
}
The following custom extention methods and helper classes were used:
using System;
using System.Windows.Forms;
using System.Collections.Generic;
using System.Xml;
namespace MyApp
{
public static class ExtensionMethods
{
public static XmlNode AppendNewElement(this XmlNode element, string name)
{
return AppendNewElement(element, name, null);
}
public static XmlNode AppendNewElement(this XmlNode element, string name, string value)
{
return AppendNewElement(element, name, value, null);
}
public static XmlNode AppendNewElement(this XmlNode element, string name, string value, params KeyValuePair<string, string>[] attributes)
{
XmlDocument doc = element.OwnerDocument ?? (XmlDocument)element;
XmlElement addedElement = doc.CreateElement(name);
if (value != null)
addedElement.SetTextValue(value);
if (attributes != null)
foreach (var attribute in attributes)
addedElement.AppendNewAttribute(attribute.Key, attribute.Value);
element.AppendChild(addedElement);
return addedElement;
}
public static XmlNode AppendNewAttribute(this XmlNode element, string name, string value)
{
XmlAttribute attr = element.OwnerDocument.CreateAttribute(name);
attr.Value = value;
element.Attributes.Append(attr);
return element;
}
}
}
namespace MyApp.Forms
{
public static class MessageBoxes
{
private static readonly string Caption = "MyApp v" + Application.ProductVersion;
public static void Alert(MessageBoxIcon icon, params object[] args)
{
MessageBox.Show(GetMessage(args), Caption, MessageBoxButtons.OK, icon);
}
public static bool YesNo(MessageBoxIcon icon, params object[] args)
{
return MessageBox.Show(GetMessage(args), Caption, MessageBoxButtons.YesNo, icon) == DialogResult.Yes;
}
private static string GetMessage(object[] args)
{
if (args.Length == 1)
{
return args[0].ToString();
}
else
{
var messegeArgs = new object[args.Length - 1];
Array.Copy(args, 1, messegeArgs, 0, messegeArgs.Length);
return string.Format(args[0] as string, messegeArgs);
}
}
}
}
The following Main method was used to allow the system to work:
[STAThread]
static void Main()
{
// Ensures that the user setting's configuration system starts in an encrypted mode, otherwise an application restart is required to change modes.
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal);
SectionInformation sectionInfo = config.SectionGroups["userSettings"].Sections["MyApp.Properties.Settings"].SectionInformation;
if (!sectionInfo.IsProtected)
{
sectionInfo.ProtectSection(null);
config.Save();
}
if (Settings.Default.UpgradePerformed == false)
Settings.Default.Upgrade();
Application.Run(new frmMain());
}
I welcome any input, critique, suggestions or improvements. I hope this helps someone somewhere.

This may not really be the answer you are looking for but it sounds like you are overcomplicating the problem by trying to manage this as an upgrade where you aren't going to continue to support the old version.
The problem isn't simply that the data type of a field is changing, the problem is that you are totally changing the business logic behind the object and need to support objects that have data relating to both old and new business logic.
Why not just continue to have a person class which has all 3 properties on it.
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
public DateTime DateOfBirth { get; set; }
}
When the user upgrades to the new version, the age is still stored, so when you access the DateOfBirth field you just check if a DateOfBirth exists, and if it doesn't you calculate it from the age and save it so when you next access it, it already has a date of birth and the age field can be ignored.
You could mark the age field as obsolete so you remember not to use it in future.
If necessary you could add some kind of private version field to the person class so internally it knows how to handle itself depending on what version it considers itself to be.
Sometimes you do have to have objects that aren't perfect in design because you still have to support data from old versions.

I know this has already been answered but I have been toying with this and wanted to add a way I handled a similar (not the same) situation with Custom Types:
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
private DateTime _dob;
public DateTime DateOfBirth
{
get
{
if (_dob is null)
{ _dob = DateTime.Today.AddYears(Age * -1); }
else { return _dob; }
}
set { _dob = value; }
}
}
If both the private _dob and public Age is null or 0, you have another issue all together. You could always set DateofBirth to DateTime.Today by default in that case. Also, if all you have is an individual's age, how will you tell their DateOfBirth down to the day?