CODEWITHSUNDEEP
c#sql-serverdapper
Arianule
Arianule

Reputation: 9053

checking for null value using dapper.net

I am using dapper to read values into an object I created where I us a basic stored procedure.

IF EXISTS(SELECT LOWER(UT.UserID) FROM UserTable UT WHERE UT.UserID = @UserId)
BEGIN
    SELECT 
    UT.UserID,
    UT.Name, 
    UT.Surname, 
    UT.TrackingString
    FROM UserTable UT
    WHERE UT.UserID = @UserId
END

and this is the code in my view model.

 IDbConnection connection;
        using (connection = new SqlConnection(ConfigurationManager.ConnectionStrings["Liberty"].ToString()))
        {
            var result = connection.QueryMultiple("GetUserData", new { UserId = userId.ToLower() }, commandType: CommandType.StoredProcedure);
            user = result.Read<UserData>().First();

        }

How can I check in the result if columns were selected.. As it is at the moment I get an InvalidOperation Exception if there is no user data(if the user does not exist).

Upvotes: 0

Views: 4940

Answers (2)

Marcus Classon
Marcus Classon

Reputation: 153

Why are you using QueryMultiple? Use Query<> instead. Then just do result.Count() before result.first(). Or do FirstOrDefault()

Might I also suggest that you create a class to receive the data?

public class User
{
    public int UserID {get; set;}
....
}

Then use connection.Query("....", new...)

Much nicer to the eyes.

Upvotes: 1

user1228
user1228

Reputation:

Use the correct Linq method. You're using one that treats no results as an invalid result, whereas your query may return no values if no such user exists.

Switch to a method that doesn't throw on no elements in the return enumerable, then check for null and handle it gracefully.

    // snip
    user = result.Read<UserData>().FirstOrDefault();
}
if(user == null)
{
    // no such user exists, go do something about it

Upvotes: 3

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