SQL Server Compact Edition ISNULL(sth, ‘ ‘) returns a boolean value?

I have an Accounts table with columns name, password and email. They are all type nvarchar. I wrote a query like

SELECT name, password, ISNULL(email, 'eeee') 
FROM Accounts 
WHERE name = '" + textBox1.Text + "' AND password ='" + textBox2.Text + "'"

I read the email as reader.getString(2) since it is nvarchar.

As I read from the internet, if email is NULL, then it should return eeee. But it says System.boolean can not be translated to System.String.

How can I correct this? Why does it return a boolean value?

Answer

According this ISNULL is not implemented in SQL Server CE. I would expect to see a syntax error raised, however.

Workaround: you can use CASE WHEN email IS NULL THEN 'eeee' ELSE email END or COALESCE. Preferably the latter.

Also use parameterised queries. If you don’t know why you should, learn.