FxCop Warnings

FxCop provides warnings that indicate rule violations in managed code libraries. The warnings are organized into rule areas such as design, localization, performance, security, and so forth. Each warning signifies a violation of an FxCop rule. This section provides in-depth discussions and examples for each FxCop warnings.

The following table shows the type of information provided for each warning:

Item Description


The TypeName for the rule.


The unique identifier for the rule.


The category of the warning.

Message Level

The importance of the issue that is identified by the rule.


The estimate of the probability that the issue is detected correctly. This value is an integer between 1 and 99.

Breaking Change

Whether the fix for a violation of the rule constitutes a breaking change. Breaking change means that an assembly that has a dependency on the target that caused the violation will not re-compile with the new fixed version or might fail at runtime because of the change. When multiple fixes are available and at least one fix is a breaking change and one fix is not, both 'Breaking' and 'Non Breaking' are specified.


The specific managed code that causes the rule to generate a warning.


Discusses the issues behind the rule.

How to Fix Violations

Explains how to change the source code to satisfy the rule and prevent it from generating a warning.

When to Exclude Warnings

Describes when it is safe to exclude a warning from the rule.

Example Code

Examples that violate the rule and "fixed" examples that satisfy the rule.

Related Warnings

Related warnings.

In This Section

Design Warnings

Warnings that support proper library design as specified by the .NET Framework Design Guidelines.

Globalization Warnings

Warnings that support world-ready libraries and applications.

Interoperability Warnings

Warnings that support interacting with COM clients.

Naming Warnings

Warnings that support adherence to the naming conventions of the .NET Framework Design Guidelines.

Performance Warnings

Warnings that support high performance libraries and applications.

Security Warnings

Warnings that support safer libraries and applications.

Usage Warnings