Blog: C# Pattern

Patterns and Its type

C# introduced pattern matching in C# 7.0. Since then, each major C# version extends pattern matching capabilities.

Declaration pattern
Type pattern
Constant pattern
Relational patterns
Logical patterns
Property pattern
Positional pattern
var pattern
Discard pattern

Declaration pattern

With a declaration pattern, you can also declare a new local variable. When a declaration pattern matches an expression, that variable is assigned a converted expression result, as the following example shows:

Type pattern

Introduced in C# 9.0, Type pattern checks the run-time type of an expression as shown below:

Constant pattern

Introduced in C# 7.0, test if an expression result equals a specified constant as shown below:

Relational pattern

Beginning with C# 9.0, you use a relational pattern to compare an expression result with a constant, as the following example shows:

Logical pattern

Beginning with C# 9.0, you use the not, and, and or pattern combinators to create the following logical patterns:

Property pattern

Beginning with C# 8.0, you use a property pattern to match an expression's properties or fields against nested patterns, as the following example shows

Positional pattern

Beginning with C# 8.0, you use a positional pattern to deconstruct an expression result and match the resulting values against the corresponding nested patterns, as the following example shows:

Var pattern

Beginning with C# 7.0, you use a var pattern to match any expression, including null, and assign its result to a new local variable, as the following example shows