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POwhy is this code causing a memory leak?
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  1. POwhy is this code causing a memory leak?
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    copied!<p>I've recently taken ownership of a WCF Windows Service that makes heavy use of the following static Utility class to retrieve lookup data:</p> <pre><code> public static class Utility { //begin code that causes increased memory consumption private static Dictionary&lt;string, ErrorData&gt; _errorData; internal static Dictionary&lt;string, ErrorData&gt; ErrorData { get { if (_errorData == null) { _errorData = GetErrorData(); } return _errorData; } } //end code that causes increased memory consumption /// GetErrorData method to get error messages from error xml /// &lt;/summary&gt; /// &lt;returns&gt;Dictionary of Error messages value for different fields.&lt;/returns&gt; internal static Dictionary&lt;string, ErrorData&gt; GetErrorData() { Dictionary&lt;string, ErrorData&gt; data = null; XmlDocument doc = LoadXmlDocument(Constants.ErrorMessagesFileName); XmlNodeList errorNode = doc.SelectNodes("/ErrorMessages/Error"); data = new Dictionary&lt;string, ErrorData&gt;(); foreach (XmlNode node in errorNode) { ErrorData errorValues = new ErrorData(); errorValues.FieldName = node.Attributes["FieldName"].Value; errorValues.ErrorMessage = node.Attributes["ErrorMessage"].Value; data.Add(node.Attributes["code"].Value, errorValues); } return data; } internal static XmlDocument LoadXmlDocument(string xmlFileName) { XmlDocument doc = null; try { if (HttpRuntime.Cache[xmlFileName] == null) { doc = new XmlDocument(); doc.Load(Constants.Folderpath + "\\" + xmlFileName); HttpRuntime.Cache.Insert(xmlFileName, doc); } else { doc = (XmlDocument)HttpRuntime.Cache[xmlFileName]; } } catch (Exception ex) { //log } return doc; } } </code></pre> <p>As you can see, the static ErrorData property makes use of a private backing field. ErrorData is a Dictionary that is constructed using an XML resource on the filesystem, which is why the contents of the file are stored in HttpRuntime.Cache upon initial retrieval. </p> <p>Under normal load, the service consumes about 120 MB of RAM.</p> <p>At some point, a team member felt the need to introduce another level of optimization by creating a static property backed by a lazily loaded static field. Anyway, the presence of said static field causes a rather severe memory leak (500MB+ ) after just a few calls to the service. </p> <p>The minute I remove the static field and property (clients instead call Utility.GetErrorData()), memory consumption goes back to normal levels.</p> <p>Can anyone explain why the presence of this static field is causing a memory leak? The WCF service is running with InstanceContextMode.PerCall, if that makes a difference.</p> <p>Many thanks.</p>
 

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