Edit & Continue lets you modify/add to your source code in break-mode while debugging without ever having to restart your debugging session.
Definitions
- Variable Capturing is the mechanism in which the lambda/delegate which is defined inline is able to hold on to any variables within its lexical scope
- Scope is the region of program text within which it is possible to refer to the entity declared by the name without qualification of the name
- Debug statement is a span of instructions delimited by subsequent sequence points. Usually a debug statement corresponds to a language statement, but it might correspond to just a part of a language statement (e.g. an opening brace of a block statement), an expression (e.g. lambda body) or other contiguous syntax (base constructor call).
- Internal active statement is a debug statement that contains a return address of a stack frame.
- Leaf active debug statement is a debug statement that contains an IP (instruction pointer) of any thread.
| Edit operation | Additional Info |
|---|---|
| Add methods, fields, constructors, properties, events, indexers, field and property initializers, nested types and top-level types (including delegates, enums, interfaces, abstract and generic types, and anonymous types) to an existing type | The existing type cannot be a generic or an interface. Adding or modifying enum members within an existing enum is not supported. |
| Add and modify iterators | Changing a regular method to an iterator method is supported |
| Add async/await expressions | Adding an await expression into an existing async method is not supported. Adding an await expression around an active statement is not supported. Changing a regular method to async is supported. |
| Modify async/await expressions | Modifying await expressions wrapped inside other expressions (e.g. G(await F());) is not supported |
| Add and modify operations with dynamic objects | - |
| Add and modify C# 6.0 language features like string interpolation and null-conditional operators | - |
| Add lambda expressions | Lambda expressions can only be added if they are static, access the “this” reference that has already been captured, or access captured variables from a single scope |
| Modify lambda expressions | The following rules guarantee that the structure of the emitted closure tree will not change--thus ensuring that lambdas in the new body are mapped to the corresponding generated CLR methods that implemented their previous versions:
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| Add LINQ expressions | LINQ expressions contain implicitly-declared anonymous functions. This means the edit rules for lambdas and LINQ will be the same. |
| Modify LINQ expressions | LINQ expressions contain implicitly-declared anonymous functions. This means the edit rules for lambdas and LINQ will be the same. |
| Modifying async lambda and LINQ expressions in combination | You can edit various nested expressions provided that they otherwise satisfy the EnC rules |
| Edit partial class * | https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#:~:text=it%20is%20now%20possible%20to%20apply%20changes%20in%20code%20that%20is%20within%20a%20partial%20class. |
| Edit Source Generated File * | https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#:~:text=you%20can%20now%20apply%20changes%20within%20a%20source%20generated)%20file. |
| Add using statement * | https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#:~:text=it%20is%20now%20possible%20to%20add%20and%2For%20change%20a%20using%20directive. |
- = As of Visual Studio 2019 Version 16.10
| Edit operation | Additional Info |
|---|---|
| Modify method signatures | - |
| Add or modify generics | - |
| Modify interfaces | - |
| Add a method body such that an abstract method becomes non-abstract | - |
| Add new abstract, virtual, or override member to a type | You CAN add a non-abstract member to an abstract type |
| Add destructor to an existing type | - |
| Modify a type parameter, base type, delegate type, or return type of an event/property/operator/indexer | - |
| Modify a catch-block if it contains an active statement (leaf or internal) | - |
| Modify a try-catch-finally block if the finally clause contains an active statement | - |
| Renaming of any kind | - |
| Delete members, types, namespaces | - |
| Delete entire method bodies | Not supported because deleting an entire method body would make the method “abstract”—which is not currently supported |
| Add using statements | Allowed in Visual Studio 2019 Version 16.10 |
| Add a namespace | - |
| Edit a member referencing an embedded interop type | - |
| Edit a member with On Error or Resume statements | Specific to Visual Basic |
| Edit a member containing an Aggregate, Group By, Simple Join, or Group Join LINQ query clause | Specific to Visual Basic |
| Edit an async method/lambda in a project that doesn't define or reference AsyncStateMachineAttribute type (e.g. projects targeting .NET Framework 4.0 and lower) | - |
| Edit an iterator method/lambda in a project that doesn't define or reference IteratorStateMachineAttribute type (e.g. projects targeting .NET Framework 4.0 and lower) | - |
| Support EnC | Do Not Support EnC |
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