Conditional expression cannot be determined error with ternary operator

Question

The following error comes with ternary operator.

Error: Type of conditional expression cannot be determined because there is no implicit conversion between '' and 'int'

Why is this error appearing even though I have specified (int)(result) for the ExecuteScalar result? How can we correct it?

CODE

    public int? GetWINFromAssociateID(int associateID)
    {
        int? WIN =null;
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            string commandText = DataLayerConstants.GetWINFromAssociateIDCommand;
            using (SqlCommand command = new SqlCommand(commandText, connection))
            {
                command.CommandType = System.Data.CommandType.Text;
                command.Parameters.AddWithValue("@payroll_svc_assoc_id", associateID);

                var result = command.ExecuteScalar();
                WIN = result == DBNull.Value ? null : (int)(result);
            }
        }
        return WIN;
    }

UPDATED REFERENCES

Read this answer and the links you'll find there: http://stackoverflow.com/a/2452375/385844 — phoog, Feb 09 '13 at 07:41

score 3 · Accepted Answer · answered Feb 09 '13 at 06:51

3

You should cast your null in ternary operator to int?:

Win=result==DBNull.Value?(int?)null:(int?)result;

answered Feb 09 '13 at 06:51

Kirill Bestemyanov

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2

It's not necessary to cast both null and result; casting either one is sufficient. – phoog Feb 09 '13 at 07:38
1

In this case it is necessary due to result has type object. – Kirill Bestemyanov Feb 09 '13 at 09:25
Ok, I was reading too hastily; my comment was only half correct. I should have written "It's not necessary to cast both `null` and `result`; casting `result` is sufficient" (because there is an implicit conversion from null to `int?`). – phoog Feb 11 '13 at 16:13

score 0 · Answer 2 · answered Feb 09 '13 at 07:42

It is because there Command.ExecuteScalar returns an instance of object type; and you may not be returning an integer.

You need to use int.Parse or better int.TryParse;

int.Parse(result.ToString());

OR

int temp = -1;
int.TryParse(result.ToString(), out temp);

Conditional expression cannot be determined error with ternary operator

2 Answers2