Help with Conversion

Hi ,
When I try this statement I get an error : Incorrect syntax near '='.
Dim AllowedUser = "Akuma" Dim query = Convert.ToInt32(db.ExecuteScalar(CommandType.Text, "SELECT COUNT(*) FROM dbo.UserAllowed WHERE Username = " & AllowedUser))
but when I try this statement: 
Dim query = Convert.ToInt32(db.ExecuteScalar(CommandType.Text, "SELECT COUNT(*) FROM dbo.UserAllowed WHERE Username = 'Akuma')) I het no error and query is =2
What's wrong with the first statement ? 

Thanks