Question about "bit" datatype

    public static bool CheckIfUserISbanned(Guid guid)
{
    StringBuilder sb = new StringBuilder();
    sb.Append("SELECT Banned");
    sb.Append(" FROM dbo.Users");
    sb.Append(" WHERE UsersID=@UserID");
    object o;
    bool isBanned = false;
    string myConnectionString = AllQuestionsPresented.connectionString;
    using (SqlConnection conn = new SqlConnection(AllQuestionsPresented.connectionString))
  开发者_运维知识库  {
        SqlCommand cmd = new SqlCommand(sb.ToString(), conn);
        conn.Open();
        cmd.Parameters.Add("@UserID", SqlDbType.UniqueIdentifier).Value = guid;
        o = cmd.ExecuteScalar();
    }

    isBanned = o == null ? false : true;//Problem here
    return isBanned;
}

The problem is that the object receives always a value which is not null. But in the Users table at the Banned field, I set its type to "Allow Nulls"... I can see that there are nulls, but no null is retreived..Something else does.. which makes the "isBanned" parameter be true..the whole time.. Why is it happening, and how can I know when the the object is bool True.

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If your database query returns NULL in SQL, this gets converted to DBNull in .NET. So rather than testing for null, test for DBNull.Value.

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You should test for DBNull.Value in your expression

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try this:

isBanned = o == null ? false : true;

also check if the string is empty or not by using string.Empty:

isBanned = o == string.Empty ? false : true;