How to check an object is empty or null

Question

1.00/5 (2 votes)

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Hi all,
this is supriya.I have a problem .In my code a function returns an object(User Defined).But i don't Know how to check whether this Object is empty or null.
My code is

SQL

txtAgeSex.Text = 
           objCommonNSBussinessObjects = objClinicalSummaryPresenter.getData(pIPno, gappln_data);
           objectToScreen(objCommonNSBussinessObjects);

private void objectToScreen(CommonNSBussinessObjects objCommonNSBussinessObjects)
        {
            txtMRNo.Text = Convert.ToString(objCommonNSBussinessObjects.mrno);
            txtRoom.Text = Convert.ToString(objCommonNSBussinessObjects.Room);
            txtWard.Text = Convert.ToString(objCommonNSBussinessObjects.Ward);
            txtAdmDate.Text = Convert.ToString(objCommonNSBussinessObjects.AdmissionDate);
            txtDocCode.Text = Convert.ToString(objCommonNSBussinessObjects.DocCode);
            txtDocName.Text = Convert.ToString(objCommonNSBussinessObjects.DocName);
            txtPatName.Text = Convert.ToString(objCommonNSBussinessObjects.PatNAme);
            txtAgeSex.Text = Convert.ToString(objCommonNSBussinessObjects.AgeSex);

        }

Here

objCommonNSBussinessObjects

is an object returned by getData(.....) method.
sometimes getData(...) returns Null Value.

i am getting an error

Object reference not set to an instance of an object.

help me in Cheking the object is empty or not

Posted 4-Sep-11 20:45pm

raj ch

Updated 4-Sep-11 20:46pm

v2

Add a Solution

3 solutions

Solution 1

C#

if (objCommonNSBussinessObjects != null)
{
  //code 
}

Posted 4-Sep-11 20:49pm

Suresh Suthar

Updated 4-Sep-11 20:55pm

v2

Comments

Abhinav S 5-Sep-11 2:59am

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-09-04T20:56:00

Solution 3

There is no such concept as "empty" for an arbitrary type; and not even "null". The object can be compared to null if:

1) This object is of the reference class, see http://msdn.microsoft.com/en-us/library/t63sy5hs%28v=VS.100%29.aspx[^];

or

2) This object is of nullable type, see http://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx[^].

Looks, before programming anything, it's advisable to read the language and .NET manual. These facts are quite elementary.

—SA

Posted 4-Sep-11 20:56pm

Sergey Alexandrovich Kryukov

Comments

Suresh Suthar 5-Sep-11 2:58am

Nice!!

Sergey Alexandrovich Kryukov 5-Sep-11 3:05am

Thank you, Suresh.
--SA

Abhinav S 5-Sep-11 3:00am

Yes correct.5.
However the OP can use null coalesce or a null check to avoid the error.

Sergey Alexandrovich Kryukov 5-Sep-11 3:06am

Thank you, Abhinav.
Using coalesce is a good syntactic sugar, good idea.
--SA

raj ch 5-Sep-11 3:29am

Thanks Abhinav. U saved me alot

Abhinav S 5-Sep-11 13:23pm

You are welcome. Or did you mean SAKryukov?
:)

Abhinav S · Accepted Answer · 2011-09-04T20:51:00

One way to avoid the error could be to use the null coalesce operator - ??.
e.g.

C#

txtMRNo.Text = Convert.ToString(objCommonNSBussinessObjects.mrno??string.empty);
txtRoom.Text = Convert.ToString(objCommonNSBussinessObjects.Room??string.empty);

Another way would be to compare your values against null.

C#

private void objectToScreen(CommonNSBussinessObjects objCommonNSBussinessObjects)
        { if (objCommonNSBussinessObjects != null){
              txtMRNo.Text = Convert.ToString(objCommonNSBussinessObjects.mrno);
              txtRoom.Text = Convert.ToString(objCommonNSBussinessObjects.Room);
              txtWard.Text = Convert.ToString(objCommonNSBussinessObjects.Ward);
              txtAdmDate.Text = Convert.ToString(objCommonNSBussinessObjects.AdmissionDate);
              txtDocCode.Text = Convert.ToString(objCommonNSBussinessObjects.DocCode);
              txtDocName.Text = Convert.ToString(objCommonNSBussinessObjects.DocName);
              txtPatName.Text = Convert.ToString(objCommonNSBussinessObjects.PatNAme);
              txtAgeSex.Text = Convert.ToString(objCommonNSBussinessObjects.AgeSex);
            }
        }