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Home > Success Center > Network Performance Monitor (NPM) > NPM - Knowledgebase Articles > Message: Unable to cast object of type 'System.DBNull' to type 'System.String'

Message: Unable to cast object of type 'System.DBNull' to type 'System.String'

Created by Kevin Twomey, last modified by Norbert Skurzewski on Apr 20, 2018

Views: 4,032 Votes: 0 Revisions: 8


The following error message is received for hosts with Problem Resource:

Unable to cast object of type 'System.DBNull' to type 'System.String'

The Web log shows the following error message:
ERROR SolarWinds.Orion.Web.UI.BaseResourceControl - Exception while loading resource

System.InvalidCastException: Unable to cast object of type 'System.DBNull' to type 'System.String'.

   at ASP.orion_vim_controls_vmobjectwithproblemsimpl_ascx.__DataBind__control5(Object sender, EventArgs e)

   at Orion_VIM_Resources_VMobjectWithProblemsImpl.ProcessLoad()

   at Orion_VIM_Resources_VMObjectWithProblemsForSummary.Page_Load(Object sender, EventArgs ea)


NPM 11.5.2



  • Consult your System Administrator before performing the following procedure. 
  • To resolve the issue you will need to delete the NULL ESX Hosts from the VIM_HOSTS table.


  1. Back up the Orion database.
  2. Open Orion Database Manager from SolarWinds Orion > Advance Features (or search in Start).
  3. Select Default Server and expand by clicking on the + sign
  4. Scroll down to VIM_Host Table.
  5. Run the following SQL Query and execute.
    where HostID = 'number of the null host'


The issue should then be resolved with the web resource.


Important Note:

The null values will affect the host if they are anywhere in columns NodeID, DataCenterID, ClusterID, ManagedObjectID, HostName, VMwareProductName, VMwareProductVersion.

Look out for any duplicate hosts, if one of the duplicates has both HostID and NodeID values, and the other host has nulls for HostID or NodeID, remove the host that has the nulls.

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