How do check byte() is null in IIF condition in vb

Question

I have a column value in Hash format in db and column datatype is varbinary(8000).I convert it into byte array.

Problem is some time this column value has null value,now in my code I want to check if column value has null value then return default value of byte array,otherwise return column value using following code

 objUser.Password_Hash = IIf(reader("Password_Hash") Is Nothing, {}, reader("Password_Hash"))

this gives error as below

System.InvalidCastException: Unable to cast object of type 'System.Byte' to type 'System.Byte[]'.

jmcilhinney · Accepted Answer · 2017-05-11 05:43:51Z

1

Firstly, don't use IIf in VB unless you're using a version so old that that the If operator doesn't exist. I think that that would mean VB 2005.

Secondly, a NULL value from a database is not Nothing in VB. It is actually an object, specifically an instance of the DBNull class, represented by the DBNull.Value field.

Thirdly, while you can compare directly to DBNull.Value if required, data readers and DataRows actually have methods dedicated specifically to testing for NULL.

So, putting it all together:

objUser.Password_Hash = If(reader.IsDBNull(reader.GetOrdinal("Password_Hash")),
                           New Byte() {},
                           DirectCast(reader("Password_Hash"), Byte()))

answered May 11, 2017 at 5:43

jmcilhinney

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