How to check if DateTime variable is not assigned?

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How to check if DateTime variable is not assigned?

I want to pass a 'Myobject' object into my function. Like this:

C#

public class Myobject
{
    public string Code { get; set; }
    public DateTime? StartDate { get; set; }

...

But.. It is possible that this object will have not assigned StartDate. So, I will get an error from SQL like this: "SqlDateTime overflow. Must be between ..."

I tried like that, but it didn't work:

C#

...

using (SqlCommand sc = new SqlCommand("AddSchedule", sqlConnection))
{
    sc.CommandType = CommandType.StoredProcedure;
    sc.CommandTimeout = 100;
    sc.Transaction = transaction;

    if (_schedule.StartDate.HasValue)
    {
        sc.Parameters.Add(new SqlParameter("@inStartDate", _schedule.StartDate));
    }
    else
    {
        sc.Parameters.Add(new SqlParameter("@inStartDate", DBNull.Value));
    }
 
    using (sc.ExecuteReader())
    {
    }

}

Please help.

----------------------------------------------------------------------------------------------------

I still can't solve that:/ This is... weird!
Once again, VERY SIMPLE code:

SQL

public class Myobject
{
    public string Code { get; set; }
    public DateTime? StartDate { get; set; }
}

and PROGRAM:
MyObject mo = new MyObject();
mo.Code= "sth";
// NO action on StartDate property! 
 
    if (mo.StartDate.HasValue)
    {
        sc.Parameters.Add(new SqlParameter("@inStartDate", mo.StartDate.Value));
    }
    else
    {
        sc.Parameters.Add(new SqlParameter("@inStartDate", DBNull.Value));
    }

mo.StartDate.HasValue returns always true...
What the hell ?

EDIT:
All I want is this 'if':
if (mo.StartDate.HasValue)
Something which tell me, if the DateTime property of the object was used or not - thats all I want. There must be an easy solution..

I even tried

C#

MyObject mo = new MyObject();

if ((mo.StartDate.Value) == null) // This returns FALSE! HOW?!
{
    sc.Parameters.Add(new SqlParameter("@inStartDate", DBNull.Value));
}

Posted 4-Jul-11 12:13pm

mnd017

Updated 5-Jul-11 3:18am

v4

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dasblinkenlight 6-Jul-11 8:22am

// This returns FALSE! HOW?!

mo.StartDate.Value is of type DateTime, which is a struct. It cannot possibly be null.

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Philippe Mori · Answer 1 · 2011-07-04T14:59:00

You also have to be aware that the range of SQL DateTime is smaller than the range of .NET type.

In particular if you are using smalldatetime, then a DateTime with it default value would out of SQL range.

For normal SQL datetime, there is a problem using DateTime.MaxValue since SQL type is less precise. After rounding to SQL precision, the value would be of of rangle since it would round to year 10000.

dasblinkenlight · Answer 2 · 2011-07-04T13:06:00

Solution 1

Try _schedule.StartDate.Value instead of _schedule.StartDate, and make sure the corresponding SP parameter is nullable.

Posted 4-Jul-11 13:06pm

dasblinkenlight

Comments

Christian Graus 4-Jul-11 19:24pm

He's doing that.

dasblinkenlight 4-Jul-11 19:38pm

Not really: _schedule.StartDate is of type Nullable<datetime>, and that's what the C# code is passing to the constructor of SqlParameter.

NDebata 4-Jul-11 23:23pm

Yes he need to pass the value, instead of the object.

Christian Graus · Answer 3 · 2011-07-04T13:25:00

You're checking if your datetime has a value, but does your SQL code also check. Use is null as in, if @date is null, to check if you were passed a null, if you need to write special case code to deal with that. The real issue is in your SP as far as I can see, you're checking and passing in a null if your value is null, so your code in C# is fine.

Sanjay J Patolia · Answer 4 · 2011-07-05T02:40:00

Solution 4

You may use StartDate = Default(DateTime)..

Posted 5-Jul-11 2:40am

Sanjay J Patolia

Comments

mnd017 5-Jul-11 8:48am

I don't understand.. how ? where?

Christian Graus · Answer 5 · 2011-07-05T11:56:00

Solution 6

Perhaps your value is not defaulting to null ? StartDate.HasValue will work. If "if (mo.StartDate.GetValueOrDefault() != DateTime.MinValue)" is working for you, then your value is defaulting to DateTime.MinValue. I'd suggest adding a constructor to your class that initialises it to null, and then using it the way you first intended. As it stands, you may as well not have a nullable object.

Posted 5-Jul-11 11:56am

Christian Graus

Comments

Dalek Dave 5-Jul-11 20:42pm

Two answers on the same question?

Gaming it?

dasblinkenlight 6-Jul-11 8:55am

This question has been edited four times. By the end of the last edit, it has become a different question.

dasblinkenlight · Answer 6 · 2011-07-06T02:28:00

Solution 7

You need to remove '@' from parameter name strings:

C#

if (_schedule.StartDate.HasValue)
    {
        sc.Parameters.Add(new SqlParameter("inStartDate", _schedule.StartDate));
    }
    else
    {
        sc.Parameters.Add(new SqlParameter("inStartDate", DBNull.Value));
    }

Posted 6-Jul-11 2:28am

dasblinkenlight

All Time Programming · Answer 7 · 2011-07-06T04:06:00

Hi mnd701,

Why do you get null in the StartDate ?
I tried the following code and it just works fine, shows the length as 19.

C#

public DateTime StartTime
{
    get;
    set;
}
private void button4_Click(object sender, EventArgs e)
{
    MessageBox.Show("StartTimeLen = " + StartTime.ToString().Length);
}

Just StartTime property is made and on a button click I display this message box, It shows me "19" as its length.

I think its not the issue that StartDate is null or doesn't have a value - by default DateTime has its min value for its each field.
As pointed by Phillipe Mori, the SQL has a low range of Date & Time and the date you get in C# doesn't fit the range of SQL & that's why you are facing error.

I recommend debug your app by displaying StartDate before passing to SQL. If you still can't make out, provide the full error message to help you better.

Thanks

How to check if DateTime variable is not assigned?

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