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POHow did I get this NullReferenceException error here right after the constructor?
 

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  1. POHow did I get this NullReferenceException error here right after the constructor?
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    <p>I've had an asp.net website running live on our intranet for a couple of weeks now. I just got an email from my application_error emailer method with an unhandled exception. </p> <p>Here it is (I've cleaned up some of the paths to make it better displayed)</p> <blockquote> <p>Exception : Object reference not set to an instance of an object. Stack Trace : at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) at TimesheetDomain.DataMappers.StaffMemberData.ReadStaff(SqlDataReader reader) in TimesheetDomain\DataMappers\StaffMemberData.cs:line 362</p> <p>at TimesheetDomain.DataMappers.StaffMemberData.GetStaffMember(String name) in TimesheetDomain\DataMappers\StaffMemberData.cs:line 401</p> <p>at TimesheetDomain.ServiceLayer.TimesheetManager.GetUserFromName(String name) in TimesheetDomain\ServiceLayer\TimesheetManager.cs:line 199 </p> <p>at UserVerification.GetCurrentUser() in \App_Code\UserVerification.cs:line 29 at WebTimesheets.OnInit(EventArgs e) in \WebTimesheets\WebTimesheets.master.cs:line 159</p> <p>at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)</p> </blockquote> <p>Basically it looks like it's erroring at my ReadStaff method which reads a data reader to build staff member objects. Here is the bit of code:</p> <pre><code>while (reader != null &amp;&amp; reader.Read()) { StaffMember newMember = null; string firstName = reader["FirstName"].ToString(); string lastName = reader["LastName"].ToString(); int staffID = (int)reader["StaffID"]; int employSection = (int)reader["EmploySection"]; StaffType employType = (StaffType)employSection; string emailAddress = reader["EmailInt"].ToString(); int employCode = (int)reader["ibbwid"]; //check if they are an admin staff member if (IsAdminStaff(employType)) { newMember = new AdminOfficer(firstName, lastName, employType, staffID, emailAddress, employCode); } else { //check if they are a supervisor if (IsASupervisor(staffID)) newMember = new Supervisor(firstName, lastName, employType, staffID, emailAddress, employCode); else newMember = new StaffMember(firstName, lastName, employType, staffID, emailAddress, employCode); } //add to identity map if (!_staffMembers.ContainsKey(staffID)) _staffMembers.Add(staffID, newMember); //****THIS IS LINE 362***** else _staffMembers[staffID] = newMember; } </code></pre> <p>(Line 362 is 3rd last line) I'm using an identity map (just read fowlers book on patterns and thought it was a good idea - may have done it wrong, happy for comments) but that's not overly relevant as later on I use the <code>newMember</code> object elsewhere so if I remove that block the <code>NullReferenceException</code> will occur.</p> <p>I am struggling to see how on earth <code>newMember</code> is null in the 3rd last line there (which is the line that errored). </p> <p>Resharper/VS doesn't give me a warning that it could be <code>null</code> - because there's the 3 constructors which I choose from. </p> <p>Can anyone suggest where I can look to try and fix this error? It's only happened once and that method has been called thousands of times since the site went live. </p> <p>Thanks</p> <p>[EDIT] As Requested, here's the IComparer for staff member</p> <pre><code>/// &lt;summary&gt; /// Comparer for staff members - compares on name /// &lt;/summary&gt; public class StaffMemberComparer : IComparer { public int Compare(object x, object y) { //check they are staff members if (x is StaffMember &amp;&amp; y is StaffMember) { //do a simple string comparison on names StaffMember staffX = x as StaffMember; StaffMember staffY = y as StaffMember; return String.Compare(staffX.FirstName, staffY.FirstName); } throw new Exception("This is for comparing Staff Members"); } } </code></pre> <p>and it's used in the IComparable implementation</p> <pre><code>/// &lt;summary&gt; /// IComparable implementaiton /// &lt;/summary&gt; /// &lt;param name="obj"&gt;object to compare to&lt;/param&gt; /// &lt;returns&gt;&lt;/returns&gt; public int CompareTo(object obj) { StaffMemberComparer comparer = new StaffMemberComparer(); return comparer.Compare(this, obj); } </code></pre>
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      1. POHow did I get this NullReferenceException error here right after the constructor?
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    1. COWhich line is TimesheetDomain\DataMappers\StaffMemberData.cs:line 362?
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      1. POHow did I get this NullReferenceException error here right after the constructor?
      1. USMatt Hamilton
    2. COThis is irrelevant to the actual question but you can replace the whole `if (!_staffMembers.ContainsKey(staffID)) _staffMembers.Add(staffID, newMember); else _staffMembers[staffID] = newMember;` with just `_staffMembers[staffID] = newMember;`. It would add the key if it doesn't already exist.
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      1. POHow did I get this NullReferenceException error here right after the constructor?
      1. USMehrdad Afshari
    3. COsorry (didn't make it very clear) the 362 line is the 3rd last line in my code block, its _staffMembers.Add(staffID, newMember); thanks mehrdad, i'll remember that, I thought I did it for a reason but can't remember it now so I'll give your version a go
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