title: Web Application Error: Sequence contains more than one element
body: <p>I have a web application that was working fine but does not work anymore. It even works on my development computer (hooked up to a local database), but not on production. So on my development computer, I change the connection string to hit the production database and I get the Error: Sequence contains more than one element.</p>
  
  <p>I believe it has to have something to do with the database, but I don't know how to figure out what it is, there are almost a thousand rows of data in it.</p>
  
  <p>Below is the linq statement that gets the data. Any ideas on how I can fix this?</p>
  
  <p>Thanks in advance</p>
  
  <pre><code>protected void lnqItems_Selecting(object sender, LinqDataSourceSelectEventArgs e)
  {
      DocksideValidationDataContext db = new DocksideValidationDataContext();
  
      DateTime startDate = (radStartDate.SelectedDate.HasValue)
          ? radStartDate.SelectedDate.Value
          : DateTime.Parse("1/1/1900");
      DateTime endDate = (radEndDate.SelectedDate.HasValue)
          ? radEndDate.SelectedDate.Value
          : DateTime.Parse("1/1/2500");
      int prevalNum = (txtSummaryFormNumber.Text.Trim() == "")
          ? -1
          : Convert.ToInt32(txtSummaryFormNumber.Text.Trim());
  
      e.Result = (from x in db.SummaryForms
                  where (x.SummaryFormId == prevalNum
                      || (prevalNum == -1)
                      &amp;&amp; (x.SampleDate &gt;= startDate.Date)
                      &amp;&amp; (x.SampleDate &lt;= endDate.Date)
                      &amp;&amp; (x.StateId == Convert.ToInt32(ddlState.SelectedValue)))
                  orderby (x.SampleDate) descending
                  select x).AsEnumerable()
                           .Select(x =&gt; new
                           {
                               x.SummaryFormId,
                               x.SampleDate,
                               DockName = x.Dock.Code + " " + x.Dock.Name,
                               Status = GetStatus(x),
                               Color = GetStatusColor(GetStatus(x))
                           })
                          .Where(x =&gt; ((prevalNum != -1
                              || cboFilter.Text == "All")
                              || (x.Status == cboFilter.Text)));
  }
  </code></pre>
  
  <p>No it occurred to me, but I didn't think it would be usefully. Here is it:</p>
  
  <pre><code>System.InvalidOperationException: Sequence contains more than one element
  
  Generated: Sat, 24 Sep 2011 15:57:41 GMT
  
  System.Web.HttpUnhandledException (0x80004005): Exception of type 'System.Web.HttpUnhandledException' was thrown. ---&gt; System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---&gt; System.InvalidOperationException: Sequence contains more than one element
     at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
     at System.Data.Linq.EntityRef`1.get_Entity()
     at Secure_SummaryForms.&lt;GetStatus&gt;b__4(SummaryFormVessel z)
     at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
     at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source)
     at Secure_SummaryForms.GetStatus(SummaryForm x)
     at Secure_SummaryForms.&lt;lnqItems_Selecting&gt;b__0(SummaryForm x)
     at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
     at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
     at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
     at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
     --- End of inner exception stack trace ---
     at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct&amp; sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
     at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
     at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
     at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
     at System.Web.UI.WebControls.QueryableDataSourceHelper.ToList(IQueryable query, Type dataObjectType)
     at System.Web.UI.WebControls.LinqDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments)
     at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback)
     at System.Web.UI.WebControls.DataBoundControl.PerformSelect()
     at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
     at System.Web.UI.WebControls.GridView.DataBind()
     at System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound()
     at System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls()
     at System.Web.UI.Control.EnsureChildControls()
     at System.Web.UI.WebControls.GridView.get_Rows()
     at Secure_SummaryForms.Page_Load(Object sender, EventArgs e)
     at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
     at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
     at System.Web.UI.Control.OnLoad(EventArgs e)
     at System.Web.UI.Control.LoadRecursive()
     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.HandleError(Exception e)
     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.ProcessRequest()
     at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
     at System.Web.UI.Page.ProcessRequest(HttpContext context)
     at ASP.secure_summaryforms_aspx.ProcessRequest(HttpContext context)
     at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
     at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously)
  
  
  Server Variables
  Name    Value
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  ALL_RAW Connection: keep-alive Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Accept-Encoding: gzip, deflate Accept-Language: en-us,en;q=0.5 Cookie: ASP.NET_SessionId=yka231rdr1r3yqv0nmbhz1nh; .POWERBASECOOKIE=5FC2CF98E578B444ACA6B75A382EAEF31EFC781DA11AF7884B360A82E544539BEC5E5BB62DD012A1D6E7005869FFF8A205D632FB724AB01EFDBED78A9A035C76B22250F8FF0BCC3AD9AB56C4EEC44C05159110DF95A6344888CB3300B642E312F3B152475CD4FA631C0000699763AE173978375D598154CE85AEF83C81E1FAF82842DF48F1D9AC97872F09FFCA33B22B; .ASPXROLES=IS-YIxYt7iXk72HXdLNE18SBwgsEd2wo3D4GfRI72jYdSmmLhUxfzBMMpFYXg5CjiowldcwSKolBjaP8jrMUgh5-rQWjQhUTY02VS3IhD5Xcav_B-d-MiaumYD-0JMWFR9-1xcP2eHQXLpnZlXzcZXhwh6G2mEDVoNZGls8MNK8bAVlo2WuTqReMmk1GTyu5duoZzh_fCs1S6AZuhWY9bwdi28kA_lfoyp4SCm2zLgNddjhbsLmgN5oopdPo9-oONS7Z5br51qYu5sS9vq-hm_TbHhHL_W7XbIKo3pJccZ1-VXkLbtIAiS_hSccjFmk1f3ttWhUnmULJVQaNNepOHofbivSEQvhQQxX-f5hpGI4K-9FqcJ-kFAjw93CrnZ2rtu6n8i3tblPEDQeAbd1JkSJjmKGpSH_4PVh1MsXNDZwSSnbBHqTaO9iKiVAvUWvANLbBxmOc3w0SfP4DUbLtl3YZVCbG_JWr5s0f5Is8scr7Nc-AxK2HEzjNVber1EofJK48eLaVJPyvm-858Yhtp5XgqMeJQUwh5l9LYeZNbc8kqxPG7kOl0Zq7q8407I230 Host: docksidevalidation.org Referer: http://docksidevalidation.org/secure/default.aspx User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:6.0.2) Gecko/20100101 Firefox/6.0.2
  APPL_MD_PATH    /LM/W3SVC/1154673598/Root
  APPL_PHYSICAL_PATH  C:\Inetpub\Websites\DocksideValidation\Website\
  AUTH_TYPE   Forms
  AUTH_USER   admin
  AUTH_PASSWORD    
  LOGON_USER   
  REMOTE_USER admin
  CERT_COOKIE  
  CERT_FLAGS   
  CERT_ISSUER  
  CERT_KEYSIZE     
  CERT_SECRETKEYSIZE   
  CERT_SERIALNUMBER    
  CERT_SERVER_ISSUER   
  CERT_SERVER_SUBJECT  
  CERT_SUBJECT     
  CONTENT_LENGTH  0
  CONTENT_TYPE     
  GATEWAY_INTERFACE   CGI/1.1
  HTTPS   off
  HTTPS_KEYSIZE    
  HTTPS_SECRETKEYSIZE  
  HTTPS_SERVER_ISSUER  
  HTTPS_SERVER_SUBJECT     
  INSTANCE_ID 1154673598
  INSTANCE_META_PATH  /LM/W3SVC/1154673598
  LOCAL_ADDR  192.168.1.131
  PATH_INFO   /secure/SummaryForms.aspx
  PATH_TRANSLATED C:\Inetpub\Websites\DocksideValidation\Website\secure\SummaryForms.aspx
  QUERY_STRING     
  REMOTE_ADDR 66.186.243.74
  REMOTE_HOST 66.186.243.74
  REMOTE_PORT 50339
  REQUEST_METHOD  GET
  SCRIPT_NAME /secure/SummaryForms.aspx
  SERVER_NAME docksidevalidation.org
  SERVER_PORT 80
  SERVER_PORT_SECURE  0
  SERVER_PROTOCOL HTTP/1.1
  SERVER_SOFTWARE Microsoft-IIS/6.0
  URL /secure/SummaryForms.aspx
  HTTP_CONNECTION keep-alive
  HTTP_ACCEPT text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
  HTTP_ACCEPT_CHARSET ISO-8859-1,utf-8;q=0.7,*;q=0.7
  HTTP_ACCEPT_ENCODING    gzip, deflate
  HTTP_ACCEPT_LANGUAGE    en-us,en;q=0.5
  HTTP_COOKIE ASP.NET_SessionId=yka231rdr1r3yqv0nmbhz1nh; .POWERBASECOOKIE=5FC2CF98E578B444ACA6B75A382EAEF31EFC781DA11AF7884B360A82E544539BEC5E5BB62DD012A1D6E7005869FFF8A205D632FB724AB01EFDBED78A9A035C76B22250F8FF0BCC3AD9AB56C4EEC44C05159110DF95A6344888CB3300B642E312F3B152475CD4FA631C0000699763AE173978375D598154CE85AEF83C81E1FAF82842DF48F1D9AC97872F09FFCA33B22B; .ASPXROLES=IS-YIxYt7iXk72HXdLNE18SBwgsEd2wo3D4GfRI72jYdSmmLhUxfzBMMpFYXg5CjiowldcwSKolBjaP8jrMUgh5-rQWjQhUTY02VS3IhD5Xcav_B-d-MiaumYD-0JMWFR9-1xcP2eHQXLpnZlXzcZXhwh6G2mEDVoNZGls8MNK8bAVlo2WuTqReMmk1GTyu5duoZzh_fCs1S6AZuhWY9bwdi28kA_lfoyp4SCm2zLgNddjhbsLmgN5oopdPo9-oONS7Z5br51qYu5sS9vq-hm_TbHhHL_W7XbIKo3pJccZ1-VXkLbtIAiS_hSccjFmk1f3ttWhUnmULJVQaNNepOHofbivSEQvhQQxX-f5hpGI4K-9FqcJ-kFAjw93CrnZ2rtu6n8i3tblPEDQeAbd1JkSJjmKGpSH_4PVh1MsXNDZwSSnbBHqTaO9iKiVAvUWvANLbBxmOc3w0SfP4DUbLtl3YZVCbG_JWr5s0f5Is8scr7Nc-AxK2HEzjNVber1EofJK48eLaVJPyvm-858Yhtp5XgqMeJQUwh5l9LYeZNbc8kqxPG7kOl0Zq7q8407I230
  HTTP_HOST   docksidevalidation.org
  HTTP_REFERER    http://docksidevalidation.org/secure/default.aspx
  HTTP_USER_AGENT Mozilla/5.0 (Windows NT 6.1; WOW64; rv:6.0.2) Gecko/20100101 Firefox/6.0.2
  
  Powered by ELMAH, version 1.1.11517.2009. Copyright (c) 2004-9, Atif Aziz. All rights reserved. Licensed under Apache License, Version 2.0.
  </code></pre>