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Missing Dispose call on local IDisposable

ID: cs/local-not-disposed
Kind: problem
Security severity: 
Severity: warning
Precision: high
Tags:
   - efficiency
   - maintainability
   - external/cwe/cwe-404
   - external/cwe/cwe-459
   - external/cwe/cwe-460
Query suites:
   - csharp-security-and-quality.qls

Click to see the query in the CodeQL repository

Objects whose type implements IDisposable should be disposed of by calling Dispose.

Recommendation

If possible, wrap the allocation of the object in a using block to automatically dispose of the object once the using block has completed.

If this is not possible, ensure that Dispose is called on the object. It is usually recommended to call Dispose within a finally block, to ensure that the object is disposed of even if an exception is thrown.

Example

In this example, a FileStream is created, but it is not disposed of.

using System;
using System.IO;

class Bad
{
    long GetLength(string file)
    {
        var stream = new FileStream(file, FileMode.Open);
        return stream.Length;
    }
}

In the revised example, a using statement is used to ensure that the file stream is properly closed.

using System;
using System.IO;

class Good
{
    long GetLength(string file)
    {
        using (var stream = new FileStream(file, FileMode.Open))
            return stream.Length;
    }
}

References

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