Document System.Security.Cryptography.Pkcs.SignedCms (#2938)

* Document System.Security.Cryptography.Pkcs.SignedCms

* Exception thrown on removal

Author: carlossanlop

xml/System.Security.Cryptography.Pkcs/SignedCms.xml

@@ -350,9 +350,10 @@
         <Parameter Name="certificate" Type="System.Security.Cryptography.X509Certificates.X509Certificate2" Index="0" FrameworkAlternate="dotnet-plat-ext-3.0" />
       </Parameters>
       <Docs>
-        <param name="certificate">To be added.</param>
-        <summary>To be added.</summary>
+        <param name="certificate">The certificate to add to the collection.</param>
+        <summary>Adds a certificate to the collection of certificates for the encoded CMS/PKCS #7 message.</summary>
         <remarks>To be added.</remarks>
+        <exception cref="T:System.Security.Cryptography.CryptographicException">The certificate already exists in the collection.</exception>
       </Docs>
     </Member>
     <Member MemberName="Certificates">
@@ -926,9 +927,10 @@ The following permissions are required to access the signature key:
         <Parameter Name="certificate" Type="System.Security.Cryptography.X509Certificates.X509Certificate2" Index="0" FrameworkAlternate="dotnet-plat-ext-3.0" />
       </Parameters>
       <Docs>
-        <param name="certificate">To be added.</param>
-        <summary>To be added.</summary>
+        <param name="certificate">The certificate to remove from the collection.</param>
+        <summary>Removes the specified certificate from the collection of certificates for the encoded CMS/PKCS #7 message.</summary>
         <remarks>To be added.</remarks>
+        <exception cref="T:System.Security.Cryptography.CryptographicException">The certificate was not found.</exception>
       </Docs>
     </Member>
     <MemberGroup MemberName="RemoveSignature">