LINQ string casting error when returning a byte array

Question

I'm trying to store hashes and salts in a database using entity framework. But when I try to call this code to return one of the salts.

var salt = (from u in db.Users
            join p in db.Passwords on u.Name equals p.UserName
            where u.Name == username
            select p.Salt).First();

I get thrown this exception: System.InvalidCastException: 'Unable to cast object of type 'System.String' to type 'System.Byte[]'.'

My Password entity looks like this:

    class Password
    {
        [Key]
        public string UserName { get; set; }
        public byte[] Hash { get; set; }
        public byte[] Salt { get; set; }
        public User User{ get; set;}
    }

What are the actual data types in your database for the columns? — gunr2171
– gunr2171, Commented Oct 13, 2020 at 16:06
What is the definition of Hash and Salt in the passwords table? — jeroenh
– jeroenh, Commented Oct 13, 2020 at 16:06
Then that is your error. Why do you define them as byte[] in code? LINQ can not magically cast string to byte[] — jeroenh
– jeroenh, Commented Oct 13, 2020 at 16:10

Tanveer Badar · Accepted Answer · 2020-10-13 16:05:24Z

2

Your table's columns are likely varchar or something similar, rather than binary/varbinary data types - or whatever term your database server uses for storing binary data.

If you are using EF core, then see value converters. There's a StringToBytesConverter available.

answered Oct 13, 2020 at 16:05

Tanveer Badar

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