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Troubleshooting data breakpoint errors (.NET)

This article helps you resolve common errors that occur when you use "Break when Value Changes."

Diagnose "Unable to set data breakpoint" errors

Important

Managed data breakpoints are supported in .NET Core 3.0, .NET 5.0.3 and later versions. You can download the latest version here.

The following errors may occur when you use managed data breakpoints. This article explains why these errors happen and provides possible solutions or workarounds to resolve them.

  • The version of .NET used by the target process does not support data breakpoints. Data breakpoints require .NET Core 3.x or .NET 5.0.3+, running on x86 or x64.

    The support for managed data breakpoints began in .NET Core 3.0. It's currently not supported in .NET Framework, versions of .NET Core under 3.0, or versions of .NET under 5.0.3.

    Solution: To solve this error, upgrade your project to .NET Core 3.x or .NET 5+.

  • The value cannot be found on the managed heap and cannot be tracked.

    • Variables declared on the stack.

      Setting data breakpoints for variables created on the stack isn't supported since these variables will be invalid once the function exits.

      Workaround: Set breakpoints on lines where the variable is used.

    • "Break when Value changes" on a variable that's not expanded from a dropdown menu.

      The debugger internally needs to know the object containing the field you want to track. The Garbage Collector may move your object around in the heap, so the debugger needs to know the object that holds the variable you wish to track.

      Workaround: If you're in a method within the object on which you want to set a data breakpoint, follow these steps:

      a. Navigate to the frame that contains the method of the object you're interested in.
      b. Open the Locals, Autos, or Watch window.
      c. Find the object and expand it to reveal its fields.
      d. Right-click the field where you want to set a data breakpoint and select Break when value changes from the context menu.

  • Data breakpoints are not supported for static fields or static properties.

    Static fields and properties aren't supported at the moment. If you're interested in this feature, provide feedback.

  • Fields and properties of structs cannot be tracked.

    Fields and properties of structs aren't supported at the moment. If you're interested in this feature, provide feedback.

  • The property value has changed and can no longer be tracked.

    A property may change how it's calculated during runtime. If this happens, the number of variables that the property depends on increases and may exceed the hardware limitation. For more information, see the following error "The property is dependent on more memory than can be tracked by the hardware."

  • The property is dependent on more memory than can be tracked by the hardware.

    Each architecture has a set number of bytes and hardware data breakpoints that it can support and the property on which you wish to set a data breakpoint has exceeded that limit. Refer to the Data breakpoint hardware limitations table to find out how many hardware-supported data breakpoints and bytes are available for the architecture you're using.

    Workaround: Set a data breakpoint on a value that may change within the property.

  • Data Breakpoints are not supported when using the legacy C# expression evaluator.

    Data breakpoints are only supported in the non-legacy C# expression evaluator.

    Solution: To disable the legacy C# expression evaluator, follow these steps:

    1. Go to the Debug menu in Visual Studio.
    2. Select Options.
    3. Navigate to Debugging > General.
    4. Uncheck the Use the legacy C# and VB expression evaluators option.

  • Class X has a custom debugger view that blocks using data breakpoints on data specific only to it.

    Data breakpoints are only supported on memory that's created by the target process (the application that's debugged). The memory on which the data breakpoint is set has been flagged as possibly owned by an object created by the DebuggerTypeProxy attribute or something else that isn't part of the target process.

    Workaround: Expand the Raw View instead of the DebuggerTypeProxy view of the object, and then set the data breakpoint. This guarantees that the data breakpoint isn't on memory owned by an object created by the DebuggerTypeProxy attribute.

Data breakpoint hardware limitations

The architecture (platform configuration) where your program runs has a limited number of hardware data breakpoints available. The following table indicates how many registers are available to use per architecture.

Architecture Number of hardware-supported data breakpoints Maximum byte size
x86 4 4
x64 4 8
ARM 1 4
ARM64 2 8

Provide feedback

For any issues or suggestions about this feature, let us know via Help > Send Feedback > Report a Problem in the IDE or the Developer Community.

See also