How do I resolve a System.Security.SecurityException with custom code in SSRS?

<system.web>

<trust level="Full"/>

</system.web>

try this in web.config

This is how I was able to solve the issue:

• strongly sign the custom assembly in question

• modify the rssrvpolicy.config file to add permissions for the assembly

                      <CodeGroup
                          class="UnionCodeGroup"
                          version="1"
                          PermissionSetName="FullTrust"
                          Name="Test"
                          Description="This code group grants the Test code full trust. ">
                          <IMembershipCondition
                                  class="StrongNameMembershipCondition"
                                  version="1"
                                  PublicKeyBlob="0024000004800000940100000602000000240000575341310004000001000100ab4b135615ca6dfd586aa0c5807b3e07fa7a02b3f376c131e0442607de792a346e64710e82c833b42c672680732f16193ba90b2819a77fa22ac6d41559724b9c253358614c270c651fad5afe9a0f8cbd1e5e79f35e0f04cb3e3b020162ac86f633cf0d205263280e3400d1a5b5781bf6bd12f97917dcdde3c8d03ee61ccba2c0"
                              />
                      </CodeGroup>
  

Side note: here is a great way to get the public key blob of your assembly VS trick for obtaining the public key token and blob of a signed assembly.