Linq Specified cast is not valid

Question

I have checked lots of posts having this error but none had this particular problem. (Also I am new to C sharp have been a java dev)

I am getting an exception as

System.InvalidCastException was caught

on the table2.Field("MEME_CK") line below in the code snippet.

There are about 3K rows in the table2, I couldn't find a way to avoid wrong casting for line table2.Field("MEME_CK")

Data can either be null, not present, valid or invalid. So I tried using nullable operator on the generic parameter cast. Also saw there is DBNull class that can possibly represent non existent value.

Is there a way to preprocess column data before doing "equals test" or joining in the code below ? How can I avoid casting even after using nullable type?

Following code basically do a join on two data tables based on MemberID i.e. MEME_CK or MemeCk and creates new object with CapHeadID, MemeCk etc as fields.

 var query =


       (from table1 in searchResult.AsEnumerable()
         join table2 in memberInfo.AsEnumerable()
         on table1.Field<decimal?>("MemeCk") equals
            table2.Field<decimal?>("MEME_CK") 
         select new
         {
              CapHeadID = table1.Field<decimal>("CapHeadID"),

             MemeCk = table1.Field<decimal>("MemeCk"),

             Suffix = table2.Field<decimal>("MEME_SFX"), 

             Suscriber = table2.Field<string>("SBSB_ID"),

              BusinessArea = table2.Field<string>("TEAM"),

             MemberName = table2.Field<string>("MemberName"),

             WorkTypeName = table1.Field<string>("WrkName"),

             SSN = table2.Field<string>("MEME_SSN"),

             AssignedUser = table1.Field<string>("AssignedUser") 

         }).Distinct().OrderBy(a => (a.Suscriber.IsNotNil() ? 

a.Suscriber : "")).Take(3000);

It would be helpful if you could explain what this code does. It seems unnecessarily convoluted. — Robert Harvey
Sorry about that. I have added the description for the code above. — amit
MEME_CK is basically a NUMBER(38,0) in table1 and Number in table2 — amit

Orion Edwards Orion Edwards · Accepted Answer · 2014-01-09T19:48:38

You're using AsEnumerable to convert the queries away from IQueryable... basically this means LINQ won't try to generate SQL code for the join, and the join will be done in C#.

With that in mind, you could try just get them as objects - like this:

from table1 in searchResult.AsEnumerable()
     join table2 in memberInfo.AsEnumerable()
     on table1.Field<object>("MemeCk") equals
        table2.Field<object>("MEME_CK") 
     select new...

I'm not sure if that will work, but it might do

Linq Specified cast is not valid

1 Answers