Dapper: execute the command several times, while linq and ToArray

Question

According to dapper docs can write

connection.Execute(@"insert into MyTable(colA, colB) values (@a, @b)", new[] { new { a=1, b=1 }, new { a=2, b=2 }, new { a=3, b=3 } } ) 

I tried to use

 conn.Execute( @" insert into RelRoleUser ( RoleID, UserID ) values( @roleID, @userID )", userroleList.Select(r => new { roleID = r.roleID, userID = r.userID }).ToArray(), null, null, null); 

But get the "Invalid type owner for DynamicMethod" exception in Dapper code

 private static Action<IDbCommand, object> CreateParamInfoGenerator(Type type) { var dm = new DynamicMethod(string.Format("ParamInfo{0}", Guid.NewGuid()), null, new[] { typeof(IDbCommand), typeof(object) }, type, true); ... 

Am I trying to write too smart code or am I misunderstood something else? Stumbled upon a mistake?

I am running Dotnet3.5 on Win7.