String Extensions

String manipulation utilities for source generators and code analysis

Extension methods for string manipulation commonly needed in source generators.

Line Splitting

Zero-allocation line enumeration using ref structs:

// Iterate lines without allocating string arrays
foreach (var entry in text.SplitLines())
{
    ReadOnlySpan<char> line = entry.Line;
    ReadOnlySpan<char> separator = entry.Separator;
    // Process line
}

// Also works with spans
ReadOnlySpan<char> span = text.AsSpan();
foreach (var line in span.SplitLines())
{
    // Process line
}

LineSplitEnumerator is a ref struct that handles \n, \r, and \r\n line endings correctly without heap allocations.

Casing Transformations

Convert between naming conventions with C# keyword handling:

// PascalCase (for property names)
"firstName".ToPropertyName()    // "FirstName"
"lastName".ToPropertyName()     // "LastName"

// camelCase (for parameter names) - escapes keywords
"FirstName".ToParameterName()   // "firstName"
"Class".ToParameterName()       // "@class"
"Object".ToParameterName()      // "@object"
"Int".ToParameterName()         // "@int"

All C# reserved keywords are automatically prefixed with @ to ensure valid identifiers.

Whitespace Normalization

Clean up generated code whitespace:

// Remove lines containing only whitespace (preserves empty lines)
text.TrimBlankLines()

// Normalize all line endings to \n (or custom)
text.NormalizeLineEndings()
text.NormalizeLineEndings("\r\n")

// Comprehensive cleanup for generated code
text.CleanWhiteSpace()
// - Strips trailing whitespace from lines
// - Collapses 3+ empty lines to 2
// - Removes empty line after { or ]
// - Removes empty line before }

// Collapse all whitespace to single spaces
text.NormalizeWhitespace()

Identifier Sanitization

Create valid C# identifiers:

// Replace non-alphanumeric with underscores
"my-api.endpoint".SanitizeIdentifier()  // "my_api_endpoint"
"namespace.class".SanitizeIdentifier()  // "namespace_class"

// Escape for string literals
"Hello \"World\"".EscapeCSharpString()  // "Hello \\\"World\\\""

Type Name Utilities

Work with fully-qualified type names:

// Strip global:: prefix
"global::System.String".StripGlobalPrefix()  // "System.String"

// Full normalization (removes global:: and trailing ?)
"global::System.String?".NormalizeTypeName()  // "System.String"

// Unwrap nullable types
"int?".UnwrapNullable()                       // "int"
"System.Nullable<int>".UnwrapNullable()       // "int"
"global::System.Nullable<System.Int32>".UnwrapNullable()  // "System.Int32"

// Conditional unwrap
typeFqn.UnwrapNullable(isOptional)  // Only unwraps if isOptional is true

// Extract short type name
"global::System.Collections.Generic.List".ExtractShortTypeName()  // "List"
"int[]".ExtractShortTypeName()  // "int[]"

C# Keyword Aliases

Map between BCL type names and C# keywords:

// Get keyword alias
"System.Int32".GetCSharpKeyword()   // "int"
"Int32".GetCSharpKeyword()          // "int"
"System.String".GetCSharpKeyword()  // "string"
"MyType".GetCSharpKeyword()         // null (no keyword)

// Compare type names (handles aliases)
"System.Int32".TypeNamesEqual("int")           // true
"global::System.String".TypeNamesEqual("string")  // true
"int".TypeNamesEqual("Int32")                  // true

Supported keywords: int, long, short, byte, sbyte, uint, ulong, ushort, float, double, decimal, bool, string, char, object, void

Type Classification

Quick type checks:

// Check for string type
typeFqn.IsStringType()  // true for "string", "String", "System.String"

// Check for primitive JSON types (no explicit serializer registration needed)
typeFqn.IsPrimitiveJsonType()
// true for: string, int, long, bool, double, decimal

Prefix/Suffix Stripping

Remove prefixes or suffixes from strings:

// Strip suffix if present
"UserEndpoints".StripSuffix("Endpoints")  // "User"
"User".StripSuffix("Endpoints")           // "User" (unchanged)

// Strip prefix if present
"I_Interface".StripPrefix("I_")  // "Interface"
"Interface".StripPrefix("I_")    // "Interface" (unchanged)

Examples

Generate Property from Field

public static void GenerateProperty(IndentedStringBuilder sb, string fieldName, string typeName)
{
    var propertyName = fieldName.StripPrefix("_").ToPropertyName();
    var paramName = propertyName.ToParameterName();

    sb.AppendLine($"public {typeName} {propertyName}");
    using (sb.BeginBlock())
    {
        sb.AppendLine($"get => {fieldName};");
        sb.AppendLine($"set => {fieldName} = value;");
    }
}

Clean Generated Output

var generatedCode = builder.ToString()
    .NormalizeLineEndings()
    .CleanWhiteSpace()
    .TrimBlankLines();

context.AddSource("Generated.g.cs", generatedCode);

Route Parameter Type Matching

// In a route parameter validator
var actualType = parameterType.ToDisplayString();
var expectedType = constraintType.NormalizeTypeName();

if (actualType.TypeNamesEqual(expectedType))
{
    // Types match (handles int vs System.Int32 vs global::System.Int32)
}

Process Code Line-by-Line

var lineCount = 0;
foreach (var entry in sourceCode.SplitLines())
{
    lineCount++;
    var trimmed = entry.Line.Trim();

    if (trimmed.StartsWith("//".AsSpan()))
    {
        // Comment line
    }
}