diff --git a/.github/prompts/error-consolidation.md b/.github/prompts/error-consolidation.md index 4d96290538393..0b3244152a8f1 100644 --- a/.github/prompts/error-consolidation.md +++ b/.github/prompts/error-consolidation.md @@ -10,9 +10,12 @@ Overall steps: ## Add a single existing file into the new consolidated article. -We're going to work through a series of files consolidating errors and warnings related to declaring the `dynamic` type and dynamic binding. +We're going to work through a series of files consolidating errors and warnings. -The destination for all these edits is the dynamic-type-and-binding-errors.md file. It already contains a skeleton for the final output. +- For the duration of this chat, all references to "destination file" refer to `using-statement-declaration-errors.md. +- For the duration of this chat, all references to "the target theme" refer to errors and warnings related to `using` statements and `using` variable declarations. Note that the `using` keyword can also be used for a `using` directive. Don't include those error messages. + +The destination file already contains a skeleton for the final output. For each source file I specify in this chat, you'll do the following tasks: @@ -28,7 +31,7 @@ For each source file I specify in this chat, you'll do the following tasks: ## Search for other related articles that may be missed. -Search all files in the docs/csharp/language-reference/compiler-messages and the docs/csharp/misc folder for any other errors and warnings that involve the `dynamic` type or dynamic binding. Give me a list to review for possible additional consolidation. Don't make any edits until the originating user approves. +Search all files in the docs/csharp/language-reference/compiler-messages and the docs/csharp/misc folder for any other errors and warnings that involve the target theme. Give me a list to review for possible additional consolidation. Don't make any edits until the originating user approves. ## Final search in roslyn source @@ -36,22 +39,22 @@ Let's check undocumented errors and the roslyn source for any missing errors. F 1. Find that number as a constant in `ErrorCodes.cs`. 2. Locate the corresponding `data` element in CSharpResources.resx. The `name` atttribute should match the number of the constant. 3. Read the error message found in the `` element that is a child of that `` element. -Give me a list of all error numbers and corresponding error messages that relate to operator overloading. +Give me a list of all error numbers and corresponding error messages that relate to the target theme. -To make sure you've found all related errors, we'll check the source. Look in `CSharpResources.resx` for any elements where the `` element is a message related to preprocessor tokens. The symbolic constant for that value is in the `name` attribute on the parent `data` element. Find that value in `ErrorCodes.cs`. It will map to the compiler error code, where the code is "CS" followed by the number as a four digit number. Build a list of any related errors, but don't make any edits yet. +To make sure you've found all related errors, we'll check the source. Look in `CSharpResources.resx` for any elements where the `` element is a message related to the target theme. The symbolic constant for that value is in the `name` attribute on the parent `data` element. Find that value in `ErrorCodes.cs`. It will map to the compiler error code, where the code is "CS" followed by the number as a four digit number. Build a list of any related errors, but don't make any edits yet. I'll give you error codes one by one. For each, I want you to do the following: -- Add the new error code to the front matter of operator-overloading-errors.md, for both the `f1_keywords` and `helpview_keywords` table. -- Add the new error code and error message to the table at the top of operator-overloading-errors.md. -- Add the new error code to the list of `displayName` elements in the TOC file for operator-overloading-errors.md. +- Add the new error code to the front matter of the destination file, for both the `f1_keywords` and `helpview_keywords` table. +- Add the new error code and error message to the table at the top of the destination file. +- Add the new error code to the list of `displayName` elements in the TOC file entry for the destination file. - Remove the new error code from the front matter in the file `csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-errors.md` file. Note that no redirections need to be added for these error codes. ## Build consolidated sections -For all remaining work, all edits will be in the `dynamic-type-and-binding-errors.md` file. The final format should mirror the structure of the `preprocessor-errors.md` file. Every H2 is a theme, all anchors are for the theme, not an individual error code. +For all remaining work, all edits will be in the target file. The final format should mirror the structure of the other target theme files in the docs/csharp/language-reference/compiler-messages folder. Every H2 is a theme, all anchors are for the theme, not an individual error code. To do that, make a new H2 section for the theme. Remove all the H2s for the individual error codes that are part of that theme. Where applicable, the new H2 can include text or examples from the H2s you remove. The new section should include links to language reference articles that discuss the feature or theme. diff --git a/.openpublishing.redirection.csharp.json b/.openpublishing.redirection.csharp.json index abe2661b9fba2..cb45587fb53be 100644 --- a/.openpublishing.redirection.csharp.json +++ b/.openpublishing.redirection.csharp.json @@ -563,6 +563,30 @@ "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8401.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/feature-version-errors" }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8410.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#implementing-idisposable-and-iasyncdisposable" + }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8417.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#implementing-idisposable-and-iasyncdisposable" + }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8418.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#implementing-idisposable-and-iasyncdisposable" + }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8647.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#using-variable-scope-and-control-flow" + }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8648.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#using-variable-scope-and-control-flow" + }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8649.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#using-variable-scope-and-control-flow" + }, { "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs8795.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/partial-types" @@ -1689,6 +1713,10 @@ "source_path_from_root": "/docs/csharp/misc/cs0244.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/unsafe-code-errors" }, + { + "source_path_from_root": "/docs/csharp/misc/cs0245.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#implementing-idisposable-and-iasyncdisposable" + }, { "source_path_from_root": "/docs/csharp/misc/cs0254.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/unsafe-code-errors" @@ -1865,6 +1893,10 @@ "source_path_from_root": "/docs/csharp/misc/cs0715.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/overloaded-operator-errors" }, + { + "source_path_from_root": "/docs/csharp/misc/cs0728.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#using-variable-scope-and-control-flow" + }, { "source_path_from_root": "/docs/csharp/misc/cs1037.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/overloaded-operator-errors" @@ -2285,6 +2317,10 @@ "source_path_from_root": "/docs/csharp/misc/cs1673.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/lambda-expression-errors#syntax-limitations-in-lambda-expressions" }, + { + "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1674.md", + "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/using-statement-declaration-errors#implementing-idisposable-and-iasyncdisposable" + }, { "source_path_from_root": "/docs/csharp/misc/cs1686.md", "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/lambda-expression-errors#syntax-limitations-in-lambda-expressions" diff --git a/docs/csharp/language-reference/compiler-messages/cs1674.md b/docs/csharp/language-reference/compiler-messages/cs1674.md deleted file mode 100644 index 50e0ac69d347b..0000000000000 --- a/docs/csharp/language-reference/compiler-messages/cs1674.md +++ /dev/null @@ -1,77 +0,0 @@ ---- -description: "Compiler Error CS1674" -title: "Compiler Error CS1674" -ms.date: 07/20/2015 -f1_keywords: - - "CS1674" -helpviewer_keywords: - - "CS1674" -ms.assetid: 7a018629-35f4-406a-8a5f-1cee7343da6d ---- -# Compiler Error CS1674 - -'T': type used in a using statement must be implicitly convertible to 'System.IDisposable' - - The [using statement](../statements/using.md) is intended to be used to ensure the disposal of an object at the end of the `using` block, thus, only types which are disposable may be used in such a statement. For example, value types are not disposable, and type parameters which are not constrained to be classes may not be assumed to be disposable. - -## Example 1 - - The following sample generates CS1674. - -```csharp -// CS1674.cs -class C -{ - public static void Main() - { - int a = 0; - a++; - - using (a) {} // CS1674 - } -} -``` - -## Example 2 - - The following sample generates CS1674. - -```csharp -// CS1674_b.cs -using System; -class C { - public void Test() { - using (C c = new C()) {} // CS1674 - } -} - -// OK -class D : IDisposable { - void IDisposable.Dispose() {} - public void Dispose() {} - - public static void Main() { - using (D d = new D()) {} - } -} -``` - -## Example 3 - - The following case illustrates the need for a class type constraint to guarantee that an unknown type parameter is disposable. The following sample generates CS1674. - -```csharp -// CS1674_c.cs -// compile with: /target:library -using System; -public class C -// Add a class type constraint that specifies a disposable class. -// Uncomment the following line to resolve. -// public class C where T : IDisposable -{ - public void F(T t) - { - using (t) {} // CS1674 - } -} -``` diff --git a/docs/csharp/language-reference/compiler-messages/cs8410.md b/docs/csharp/language-reference/compiler-messages/cs8410.md deleted file mode 100644 index 781c229fdaaa4..0000000000000 --- a/docs/csharp/language-reference/compiler-messages/cs8410.md +++ /dev/null @@ -1,44 +0,0 @@ ---- -description: "Learn more about: Compiler Error CS8410" -title: Compiler Error CS8410 -ms.date: 07/11/2020 -f1_keywords: - - "CS8410" -helpviewer_keywords: - - "CS8410" -author: Youssef1313 ---- -# Compiler Error CS8410 - -'type': type used in an asynchronous `using` statement must be implicitly convertible to 'System.IAsyncDisposable' or implement a suitable 'DisposeAsync' method. - -The expression inside an `await using` statement must have a `DisposeAsync` method. - -## To correct this error - -Remove the `await using` keywords, or implement a suitable `DisposeAsync` method. - -## Example - -```csharp -using System.Threading.Tasks; - -class Program -{ - static async Task Main() - { - // error CS8410: 'Example': type used in an asynchronous using statement - // must be implicitly convertible to 'System.IAsyncDisposable' or implement - // a suitable 'DisposeAsync' method. - await using var example = new Example(); - } -} - -class Example -{ -} -``` - -## See also - -- [Implement a DisposeAsync method](../../../standard/garbage-collection/implementing-disposeasync.md) diff --git a/docs/csharp/language-reference/compiler-messages/using-statement-declaration-errors.md b/docs/csharp/language-reference/compiler-messages/using-statement-declaration-errors.md new file mode 100644 index 0000000000000..3724a15b661aa --- /dev/null +++ b/docs/csharp/language-reference/compiler-messages/using-statement-declaration-errors.md @@ -0,0 +1,126 @@ +--- +title: Resolve errors related to `using` statements and `using` declarations +description: These errors indicate an incorrect use of the `using` statement or `using` declarations. Learn about the errors and how to fix them. +f1_keywords: + - "CS0245" + - "CS0728" + - "CS1674" + - "CS8410" + - "CS8417" + - "CS8418" + - "CS8647" + - "CS8648" + - "CS8649" + - "CS9229" +helpviewer_keywords: + - "CS0245" + - "CS0728" + - "CS1674" + - "CS8410" + - "CS8417" + - "CS8418" + - "CS8647" + - "CS8648" + - "CS8649" + - "CS9229" +ms.date: 10/27/2025 +ai-usage: ai-assisted +--- +# Resolve warnings related to the `using` statements and `using` declarations + +This article covers the following compiler errors: + + +- [**CS0245**](#implementing-idisposable-and-iasyncdisposable): *Destructors and `object.Finalize` cannot be called directly. Consider calling `IDisposable.Dispose` if available.* +- [**CS0728**](#using-variable-scope-and-control-flow): *Possibly incorrect assignment to local variable which is the argument to a using or `lock` statement. The `Dispose` call or unlocking will happen on the original value of the local.* +- [**CS1674**](#implementing-idisposable-and-iasyncdisposable): *Type used in a using statement must be implicitly convertible to '`System.IDisposable`'.* +- [**CS8410**](#implementing-idisposable-and-iasyncdisposable): *'Type used in an asynchronous `using` statement must be implicitly convertible to '`System.IAsyncDisposable`' or implement a suitable '`DisposeAsync`' method.* +- [**CS8417**](#implementing-idisposable-and-iasyncdisposable): *Type used in an asynchronous using statement must implement '`System.IAsyncDisposable`' or implement a suitable '`DisposeAsync`' method. Did you mean '`using`' rather than '`await using`'?* +- [**CS8418**](#implementing-idisposable-and-iasyncdisposable): *Type used in a using statement must implement '`System.IDisposable`'. Did you mean '`await using`' rather than 'using'?* +- [**CS8647**](#using-variable-scope-and-control-flow): *A using variable cannot be used directly within a switch section (consider using braces).* +- [**CS8648**](#using-variable-scope-and-control-flow): *A `goto` cannot jump to a location after a using declaration.* +- [**CS8649**](#using-variable-scope-and-control-flow): *A `goto` cannot jump to a location before a using declaration within the same block.* +- [**CS9229**](#incorrect-using-declaration): *Modifiers cannot be placed on using declarations.* + +## Implementing IDisposable and IAsyncDisposable + +The following compiler errors and warnings indicate issues with implementing or using the dispose pattern: + +- **CS0245**: *Destructors and `object.Finalize` cannot be called directly. Consider calling `IDisposable.Dispose` if available.* +- **CS1674**: *Type used in a using statement must be implicitly convertible to '`System.IDisposable`'.* +- **CS8410**: *Type used in an asynchronous `using` statement must be implicitly convertible to '`System.IAsyncDisposable`' or implement a suitable 'DisposeAsync' method.* +- **CS8417**: *Type used in an asynchronous `using` statement must implement '`System.IAsyncDisposable`' or implement a suitable '`DisposeAsync`' method. Did you mean '`using`' rather than '`await using`'?* +- **CS8418**: *Type used in a using statement must implement '`System.IDisposable`'. Did you mean '`await using`' rather than '`using`'?* + +The [using statement](../statements/using.md) ensures proper disposal of resources at the end of the `using` block. To use a type with a `using` statement, it must implement the appropriate disposal interface. For synchronous `using` statements, the type must implement . For asynchronous `await using` statements, the type must implement . + +- **Cannot call Finalize directly (CS0245)**: You can't directly call a destructor or the method. The garbage collector automatically invokes finalizers when objects are no longer referenced. For deterministic cleanup, implement and call the `Dispose` method instead. +- **Type must implement IDisposable (CS1674)**: Only types that implement can be used in a `using` statement. Value types don't implement this interface, and generic type parameters without proper constraints can't be assumed to be disposable. Apply a type constraint like `where T : IDisposable` when working with generic types. +- **Type must implement IAsyncDisposable (CS8410)**: Types used with `await using` must implement or provide a suitable `DisposeAsync` method. If your type doesn't support asynchronous disposal, use a synchronous `using` statement instead or implement the required interface. +- **Mismatched disposal pattern (CS8417, CS8418)**: CS8417 occurs when you use `await using` with a type that only implements . CS8418 occurs when you use synchronous `using` with a type that only implements . Match the `using` keyword to the interface your type implements, or implement both interfaces if you need to support both patterns. + +For more information, see [Finalizers](../../programming-guide/classes-and-structs/finalizers.md), [Implement a Dispose method](../../../standard/garbage-collection/implementing-dispose.md), and [Implement a DisposeAsync method](../../../standard/garbage-collection/implementing-disposeasync.md). + +## Using variable scope and control flow + +The following compiler errors and warnings relate to incorrect usage of `using` variables within control flow statements: + +- **CS0728**: *Possibly incorrect assignment to local variable which is the argument to a `using` or `lock` statement. The `Dispose` call or unlocking will happen on the original value of the local.* +- **CS8647**: *A using variable cannot be used directly within a switch section (consider using braces).* +- **CS8648**: *A `goto` cannot jump to a location after a using declaration.* +- **CS8649**: *A `goto` cannot jump to a location before a using declaration within the same block.* + +Variables declared with `using` have specific scoping rules that prevent resource leaks. The compiler enforces these rules to ensure proper disposal. + +- **Assignment to using variable (CS0728)**: This warning indicates you assigned a new value to a variable that's the resource in a `using` statement. The dispose call occurs on the original value, not the newly assigned value, which can lead to resource leaks. Initialize the resource in the `using` statement declaration instead of assigning to it later. + +- **Using variable in switch section (CS8647)**: A `using` declaration creates a variable that's disposed at the end of its scope. When used directly in a switch section without braces, the scope is ambiguous and can lead to errors. Wrap the switch section content in braces to clearly define the scope. + +- **Goto statements and using declarations (CS8648, CS8649)**: You can't use `goto` statements to jump over `using` declarations because jumping would skip proper resource management. CS8648 occurs when jumping forward over a `using` declaration, and CS8649 occurs when jumping backward to a location before a `using` declaration. Restructure your code to use structured control flow like loops, or move the `using` declaration outside the jump target. + +For more information, see [using statement](../statements/using.md). + +## Incorrect `using` declaration + +- **CS9229**: *Modifiers cannot be placed on using declarations.* + +A variable declaration wrapped in a `using` declaration can't include any of the following modifiers: + +- `const` +- `static` +- `volatile` +- `readonly` +- Accessibility modifiers: `public`, `protected`, `internal`, `private`, `protected internal`, or `private protected` + +The following example generates CS9229: + +```csharp +using System; + +class Program +{ + static void Main() + { + // error CS9229: Modifiers cannot be placed on using declarations. + public using var resource = new Resource(); + + // error CS9229: Modifiers cannot be placed on using declarations. + static using var anotherResource = new Resource(); + } +} + +class Resource : IDisposable +{ + public void Dispose() { } +} +``` + +To correct this error, remove the modifier from the `using` declaration: + +```csharp +using var resource = new Resource(); +``` + +For more information, see [using statement](../statements/using.md). diff --git a/docs/csharp/language-reference/toc.yml b/docs/csharp/language-reference/toc.yml index 8a866c5b23fe1..af8606c9862e8 100644 --- a/docs/csharp/language-reference/toc.yml +++ b/docs/csharp/language-reference/toc.yml @@ -604,6 +604,10 @@ items: CS0105, CS0138, CS0431, CS0432, CS0440, CS0576, CS0687, CS1529, CS1537, CS7000, CS7007, CS8019, CS8083, CS8085, CS8914, CS8915, CS8933, CS9055, CS9130, CS9131, CS9132, CS9133, CS9162, CS9163 + - name: Using statements and declarations + href: ./compiler-messages/using-statement-declaration-errors.md + displayName: > + CS0245, CS0728, CS1674, CS8410, CS8417, CS8418, CS8647, CS8648, CS8649, CS9229 - name: Source generators href: ./compiler-messages/source-generator-errors.md displayName: > @@ -1631,8 +1635,6 @@ items: href: ../misc/cs1671.md - name: CS1672 href: ../misc/cs1672.md - - name: CS1674 - href: ./compiler-messages/cs1674.md - name: CS1675 href: ../misc/cs1675.md - name: CS1676 @@ -1907,8 +1909,6 @@ items: href: ./compiler-messages/cs8355.md - name: CS8403 href: ./compiler-messages/cs8403.md - - name: CS8410 - href: ./compiler-messages/cs8410.md - name: CS8411 href: ./compiler-messages/cs8411.md - name: CS8422 diff --git a/docs/csharp/misc/cs0245.md b/docs/csharp/misc/cs0245.md deleted file mode 100644 index 3881c1aeb9d3f..0000000000000 --- a/docs/csharp/misc/cs0245.md +++ /dev/null @@ -1,43 +0,0 @@ ---- -description: "Compiler Error CS0245" -title: "Compiler Error CS0245" -ms.date: 07/20/2015 -f1_keywords: - - "CS0245" -helpviewer_keywords: - - "CS0245" -ms.assetid: 3f2beb2f-a510-4568-9d11-bb1f65066acd ---- -# Compiler Error CS0245 - -Destructors and object.Finalize cannot be called directly. Consider calling IDisposable.Dispose if available. - - For more information, see [Programming Essentials for Garbage Collection](../../standard/garbage-collection/index.md) and [Finalizers](../programming-guide/classes-and-structs/finalizers.md). - - The following sample generates CS0245: - -```csharp -// CS0245.cs -using System; -using System.Collections; - -class MyClass // : IDisposable -{ - /* - public void Dispose() - { - // cleanup code goes here - } - */ - - void m() - { - this.Finalize(); // CS0245 - // this.Dispose(); - } - - public static void Main() - { - } -} -``` diff --git a/docs/csharp/misc/cs0728.md b/docs/csharp/misc/cs0728.md deleted file mode 100644 index 460d33cca7ecd..0000000000000 --- a/docs/csharp/misc/cs0728.md +++ /dev/null @@ -1,69 +0,0 @@ ---- -description: "Compiler Warning (level 2) CS0728" -title: "Compiler Warning (level 2) CS0728" -ms.date: 07/20/2015 -f1_keywords: - - "CS0728" -helpviewer_keywords: - - "CS0728" -ms.assetid: ad6d860d-bac4-48f3-9eab-1efd2b6de6c0 ---- -# Compiler Warning (level 2) CS0728 - -Possibly incorrect assignment to local 'variable' which is the argument to a using or lock statement. The Dispose call or unlocking will happen on the original value of the local. - - There are several scenarios where `using` or `lock` blocks will result in a temporary leak of resources. Here is one example: - - `thisType f = null;` - - `using (f)` - - `{` - - `f = new thisType();` - - `...` - - `}` - - In this case, the original value, such as null, of the variable `thisType` will be disposed of when the `using` block finishes executing, but the `thisType` object created inside the block will not be, although it will eventually get garbage collected. - - To resolve this error, use the following form: - - `using (thisType f = new thisType())` - - `{` - - `...` - - `}` - - In this case, the newly allocated `thisType` object will be disposed of. - -## Example - - The following code will generate warning CS0728. - -```csharp -// CS0728.cs - -using System; -public class ValidBase : IDisposable -{ - public void Dispose() { } -} - -public class Logger -{ - public static void dummy() - { - ValidBase vb = null; - using (vb) - { - vb = null; // CS0728 - } - vb = null; - } - public static void Main() { } -} -``` diff --git a/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md b/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md index 0e67559e90914..e33a9a15c0a6d 100644 --- a/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md +++ b/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md @@ -302,8 +302,6 @@ f1_keywords: - "CS8413" - "CS8414" - "CS8415" - - "CS8417" - - "CS8418" - "CS8419" - "CS8420" - "CS8421" @@ -335,9 +333,6 @@ f1_keywords: - "CS8635" - "CS8641" - "CS8646" - - "CS8647" - - "CS8648" - - "CS8649" - "CS8650" - "CS8651" - "CS8656" @@ -552,8 +547,6 @@ f1_keywords: - "CS9095" - "CS9096" - "CS9097" -# C# 12 errors begin here - - "CS9229" # Modifiers cannot be placed on using declarations (using declarations) # C# 14 errors begin here - "CS9327" - "CS9328"