> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # C# Default The `default` operator in C# produces the default value of a specified type. It evaluates the memory allocation for a type and returns its zero-initialized state, which translates to a null reference for reference types and a zeroed bit-pattern for value types. ## Syntax The operator supports two syntactical forms: the explicit `default(T)` expression and the inferred `default` literal (introduced in C# 7.1). ```csharp theme={"dark"} // Explicit type specification TypeName explicitVariable = default(TypeName); // Target-typed default literal (type is inferred from the declaration) TypeName inferredVariable = default; ``` ## Type Resolution Mechanics The exact value produced by the `default` operator depends strictly on the Common Type System (CTS) classification of the target type: * **Reference Types (`class`, `interface`, `delegate`, `string`, `dynamic`):** Evaluates to `null`. * **Numeric Value Types (`int`, `double`, `decimal`, etc.):** Evaluates to `0` (or `0.0`, `0m`). * **Boolean (`bool`):** Evaluates to `false`. * **Structs (Custom Value Types):** Evaluates to an instance of the struct where all underlying fields are recursively set to their own default values. * **Enums:** Evaluates to the enumeration member backed by the integer value `0`. If no member explicitly defines `0`, it still evaluates to `0` cast to the enum type. * **Nullable Value Types (`Nullable` or `T?`):** Evaluates to `null`, which structurally represents an instance where the `HasValue` property is `false`. ## Syntax Visualization ```csharp theme={"dark"} // Value Types int defaultInt = default; // 0 double defaultDouble = default; // 0.0 bool defaultBool = default; // false char defaultChar = default; // '\0' (U+0000) // Reference Types string defaultString = default; // null object defaultObject = default; // null // Complex Types DateTime defaultDate = default; // 01/01/0001 00:00:00 (DateTime.MinValue) Guid defaultGuid = default; // 00000000-0000-0000-0000-000000000000 // Nullable Value Types int? defaultNullable = default; // null ``` ## Behavior in Generic Contexts When applied to an unconstrained generic type parameter `T`, the `default` operator defers resolution until runtime. The compiler cannot determine whether `T` will be a reference type or a value type, so `default` or `default(T)` guarantees safe initialization regardless of the substituted type argument. ```csharp theme={"dark"} public class GenericContainer { public T DefaultProperty { get; } = default; public T GetDefaultValue() { return default(T); } } ``` ## Target-Typed Evaluation Rules When using the `default` literal (without the parentheses and type name), the C# compiler must be able to infer the target type from the surrounding expression context. ```csharp theme={"dark"} // Valid: Type inferred from variable declaration int number = default; // Valid: Type inferred from method signature void Process(string input) { } Process(default); // Valid: Type inferred from return type bool IsValid() => default; // Invalid: Cannot infer type (results in compiler error CS0815) var unknown = default; ```

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