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Add Roslyn source generator samples with attribute-based member generation and CSV-to-C# generation
Co-authored-by: agocke <515774+agocke@users.noreply.github.com>
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‎csharp/roslyn-sdk/SourceGenerators/CsvGenerator/CsvGenerator/CsvGenerator.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<TargetFramework>netstandard2.0</TargetFramework>
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<LangVersion>latest</LangVersion>
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<EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.10.0" PrivateAssets="all" />
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<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
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</ItemGroup>
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</Project>

‎csharp/roslyn-sdk/SourceGenerators/CsvGenerator/CsvGenerator/CsvIncrementalGenerator.cs‎

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#nullable enable
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using System.Collections.Immutable;
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using System.IO;
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using System.Linq;
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using System.Text;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.Text;
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namespace CsvGenerator;
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/// <summary>
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/// A source generator that reads <c>.csv</c> additional files and produces a
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/// strongly-typed C# class for each one. The first row of the CSV is treated
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/// as column headers (property names) and every subsequent row becomes a static
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/// instance exposed through a generated <c>All</c> property.
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/// </summary>
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[Generator]
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public class CsvIncrementalGenerator : IIncrementalGenerator
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{
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public void Initialize(IncrementalGeneratorInitializationContext context)
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{
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// Filter additional files to only .csv files.
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IncrementalValuesProvider<AdditionalText> csvFiles =
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context.AdditionalTextsProvider
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.Where(static file => Path.GetExtension(file.Path)
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.Equals(".csv", System.StringComparison.OrdinalIgnoreCase));
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// Read file content and pair with file name.
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IncrementalValuesProvider<(string ClassName, string Text)?> csvData =
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csvFiles.Select(static (file, ct) =>
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{
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string? text = file.GetText(ct)?.ToString();
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if (text is null)
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return null;
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string className = Path.GetFileNameWithoutExtension(file.Path);
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return ((string ClassName, string Text)?)(className, text);
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});
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// Generate source for each CSV file.
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context.RegisterSourceOutput(csvData, static (spc, csv) =>
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{
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if (csv is null)
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return;
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string? source = GenerateClassFromCsv(csv.Value.ClassName, csv.Value.Text);
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if (source is not null)
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{
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spc.AddSource($"{csv.Value.ClassName}.g.cs", SourceText.From(source, Encoding.UTF8));
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}
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});
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}
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private static string? GenerateClassFromCsv(string className, string csvText)
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{
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string[] lines = csvText.Split(new[] { "\r\n", "\n" }, System.StringSplitOptions.RemoveEmptyEntries);
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if (lines.Length < 2) // Need at least a header and one data row.
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return null;
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string[] headers = ParseCsvLine(lines[0]);
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if (headers.Length == 0)
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return null;
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var sb = new StringBuilder();
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sb.AppendLine("// <auto-generated />");
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sb.AppendLine();
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sb.AppendLine("namespace CsvGenerated");
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sb.AppendLine("{");
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sb.AppendLine($" /// <summary>Strongly-typed class generated from {className}.csv.</summary>");
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sb.AppendLine($" public sealed class {className}");
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sb.AppendLine(" {");
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// Properties (all strings for simplicity)
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foreach (string header in headers)
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{
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sb.AppendLine($" public string {SanitizeIdentifier(header)} {{ get; }}");
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}
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sb.AppendLine();
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// Constructor
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sb.Append($" private {className}(");
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sb.Append(string.Join(", ", headers.Select(h => $"string {CamelCase(SanitizeIdentifier(h))}")));
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sb.AppendLine(")");
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sb.AppendLine(" {");
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foreach (string header in headers)
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{
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string prop = SanitizeIdentifier(header);
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sb.AppendLine($" {prop} = {CamelCase(prop)};");
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}
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sb.AppendLine(" }");
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sb.AppendLine();
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// All property – static list of rows
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sb.AppendLine(" /// <summary>All rows from the CSV data.</summary>");
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sb.AppendLine($" public static global::System.Collections.Generic.IReadOnlyList<{className}> All {{ get; }} =");
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sb.AppendLine($" new {className}[]");
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sb.AppendLine(" {");
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for (int i = 1; i < lines.Length; i++)
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{
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string[] values = ParseCsvLine(lines[i]);
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// Pad or trim to match header count.
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string[] row = new string[headers.Length];
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for (int j = 0; j < headers.Length; j++)
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{
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row[j] = j < values.Length ? values[j] : string.Empty;
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}
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sb.Append($" new {className}(");
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sb.Append(string.Join(", ", row.Select(EscapeString)));
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sb.AppendLine("),");
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}
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sb.AppendLine(" };");
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// ToString override
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sb.AppendLine();
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sb.AppendLine(" public override string ToString() =>");
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sb.Append(" $\"");
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sb.Append(string.Join(", ", headers.Select(h =>
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{
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string prop = SanitizeIdentifier(h);
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return $"{prop}={{{prop}}}";
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})));
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sb.AppendLine("\";");
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sb.AppendLine(" }");
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sb.AppendLine("}");
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return sb.ToString();
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}
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private static string[] ParseCsvLine(string line)
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{
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// Simple CSV parser – handles quoted fields but not escaped quotes inside quotes.
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var fields = new System.Collections.Generic.List<string>();
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var current = new StringBuilder();
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bool inQuotes = false;
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for (int i = 0; i < line.Length; i++)
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{
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char c = line[i];
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if (c == '"')
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{
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inQuotes = !inQuotes;
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}
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else if (c == ',' && !inQuotes)
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{
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fields.Add(current.ToString().Trim());
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current.Clear();
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}
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else
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{
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current.Append(c);
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}
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}
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fields.Add(current.ToString().Trim());
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return fields.ToArray();
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}
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private static string SanitizeIdentifier(string name)
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{
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var sb = new StringBuilder();
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foreach (char c in name)
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{
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if (char.IsLetterOrDigit(c) || c == '_')
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sb.Append(c);
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}
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string result = sb.ToString();
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if (result.Length == 0)
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return "_";
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// Ensure starts with letter or underscore.
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if (char.IsDigit(result[0]))
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result = "_" + result;
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// PascalCase first letter.
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return char.ToUpperInvariant(result[0]) + result.Substring(1);
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}
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private static string CamelCase(string name)
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{
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if (name.Length == 0)
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return name;
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return char.ToLowerInvariant(name[0]) + name.Substring(1);
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}
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private static string EscapeString(string value) =>
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$"\"{value.Replace("\\", "\\\\").Replace("\"", "\\\"")}\"";
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}

‎csharp/roslyn-sdk/SourceGenerators/CsvGenerator/CsvGeneratorDemo/CsvGeneratorDemo.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net8.0</TargetFramework>
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<Nullable>enable</Nullable>
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<ImplicitUsings>enable</ImplicitUsings>
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</PropertyGroup>
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<ItemGroup>
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<ProjectReference Include="..\CsvGenerator\CsvGenerator.csproj"
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OutputItemType="Analyzer"
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ReferenceOutputAssembly="false" />
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</ItemGroup>
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<!-- Expose .csv files as additional files to the source generator -->
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<ItemGroup>
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<AdditionalFiles Include="Data\*.csv" />
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</ItemGroup>
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</Project>

‎csharp/roslyn-sdk/SourceGenerators/CsvGenerator/CsvGeneratorDemo/Data/Cities.csv‎

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Name,Country,Population
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Tokyo,Japan,13960000
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Delhi,India,11030000
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Shanghai,China,24870000
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São Paulo,Brazil,12330000
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Mexico City,Mexico,9210000

‎csharp/roslyn-sdk/SourceGenerators/CsvGenerator/CsvGeneratorDemo/Program.cs‎

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// Demonstrate using the strongly-typed class generated from Cities.csv.
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using CsvGenerated;
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Console.WriteLine("=== Cities loaded from CSV ===");
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Console.WriteLine();
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foreach (Cities city in Cities.All)
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{
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Console.WriteLine(city);
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}
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Console.WriteLine();
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Console.WriteLine($"Total cities: {Cities.All.Count}");

‎csharp/roslyn-sdk/SourceGenerators/CsvGenerator/README.md‎

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---
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languages:
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- csharp
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products:
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- dotnet
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page_type: sample
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name: "CSV to C# Source Generator"
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urlFragment: "roslyn-csv-generator"
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description: "A Roslyn incremental source generator that compiles CSV files into strongly-typed C# classes at build time."
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---
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# CsvGenerator – Non-C# File to C# Source Generator
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This sample demonstrates how to write an [incremental source generator](https://learn.microsoft.com/dotnet/csharp/roslyn-sdk/source-generators-overview) that reads a non-C# source file (CSV) and generates C# code from it at compile time.
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## What it does
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The generator scans for `.csv` files registered as `AdditionalFiles` in the project. For each CSV file it finds, it generates a strongly-typed C# class where:
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- The **first row** is treated as column headers, which become property names.
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- Each **subsequent row** becomes a static instance accessible through a generated `All` property.
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- A `ToString()` override is generated for easy display.
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## Project structure
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| Project | Description |
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|---------|-------------|
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| `CsvGenerator` | The source generator (targets `netstandard2.0`). |
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| `CsvGeneratorDemo` | A console application that uses the generator with a sample CSV file. |
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## How CSV files are exposed to the generator
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In the demo project's `.csproj`, CSV files are included as additional files:
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```xml
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<ItemGroup>
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<AdditionalFiles Include="Data\*.csv" />
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</ItemGroup>
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```
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## Running
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```bash
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dotnet run --project CsvGeneratorDemo
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```
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### Expected output
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```text
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=== Cities loaded from CSV ===
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Name=Tokyo, Country=Japan, Population=13960000
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Name=Delhi, Country=India, Population=11030000
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Name=Shanghai, Country=China, Population=24870000
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Name=São Paulo, Country=Brazil, Population=12330000
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Name=Mexico City, Country=Mexico, Population=9210000
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Total cities: 5
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```

‎csharp/roslyn-sdk/SourceGenerators/GenerateMembers/GenerateMembersDemo/GenerateMembersDemo.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net8.0</TargetFramework>
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<Nullable>enable</Nullable>
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<ImplicitUsings>enable</ImplicitUsings>
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</PropertyGroup>
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<ItemGroup>
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<ProjectReference Include="..\GenerateMembersGenerator\GenerateMembersGenerator.csproj"
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OutputItemType="Analyzer"
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ReferenceOutputAssembly="false" />
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</ItemGroup>
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</Project>

‎csharp/roslyn-sdk/SourceGenerators/GenerateMembers/GenerateMembersDemo/Program.cs‎

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using GenerateMembersGenerator;
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// Apply the [GenerateMembers] attribute so the source generator creates
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// a Describe() method and a PropertyNames list for this type.
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var person = new Person { FirstName = "Alice", LastName = "Smith", Age = 30 };
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Console.WriteLine(person.Describe());
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Console.WriteLine("Properties:");
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foreach (string name in Person.PropertyNames)
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{
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Console.WriteLine($" {name}");
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}
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[GenerateMembers]
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public partial class Person
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{
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public string FirstName { get; set; } = string.Empty;
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public string LastName { get; set; } = string.Empty;
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public int Age { get; set; }
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}

‎csharp/roslyn-sdk/SourceGenerators/GenerateMembers/GenerateMembersGenerator/GenerateMembersGenerator.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<TargetFramework>netstandard2.0</TargetFramework>
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<LangVersion>latest</LangVersion>
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<EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.10.0" PrivateAssets="all" />
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<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
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</ItemGroup>
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</Project>

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