C# 關鍵字C# Keywords
關鍵字是預先定義的保留識別項，它對編譯器具有特殊意義。Keywords are predefined, reserved identifiers that have special meanings to the compiler. 您必須在關鍵字加上 @ 做為前置詞，才能將它們當做程式中的識別項使用。They cannot be used as identifiers in your program unless they include @ as a prefix. 例如，@if 是有效的識別項，但 if 不是，因為 if 是關鍵字。For example, @if is a valid identifier, but if is not because if is a keyword.
本主題中的第一個表格列出在 C# 程式的任何部分中為保留識別項的關鍵字。The first table in this topic lists keywords that are reserved identifiers in any part of a C# program. 本主題中的第二個表格列出 C# 中的內容關鍵字。The second table in this topic lists the contextual keywords in C#. 內容關鍵字只在有限的程式內容中具有特殊意義，並且可在該內容以外的地方用來當做識別項。Contextual keywords have special meaning only in a limited program context and can be used as identifiers outside that context. 一般而言，將新的關鍵字加入至 C# 語言時，會以內容關鍵字加入它們，以避免中斷利用舊版本撰寫的程式。Generally, as new keywords are added to the C# language, they are added as contextual keywords in order to avoid breaking programs written in earlier versions.
內容關鍵字Contextual keywords
內容關鍵字可用來在程式碼中提供特定的意義，但它不是 C# 中的保留字。A contextual keyword is used to provide a specific meaning in the code, but it is not a reserved word in C#. 某些內容關鍵字 (例如 partial 和 where) 在兩個以上的內容中具有特殊意義。Some contextual keywords, such as partial and where, have special meanings in two or more contexts.