how compare a binary(max) value saved in sql to know is it null, in C#?

Question

I am saving photo in SQL (varbinary(MAX) Data Type) with this code:

                    if (SPV1 == true)
                    {
                        imgVC1 = Image.FromFile(Open1.FileName);
                        imgFormat1 = picVisit1.BackgroundImage.RawFormat;
                        Ms1 = new MemoryStream();
                        imgVC1.Save(Ms1, imgFormat1);
                        byte[] ArrayV1 = Ms1.GetBuffer();

                        csCompanies.VisitCard1 = ArrayV1;
                    }
                    else                                                
                        csCompanies.VisitCard1 = null;

and it continues with this code in Class:

            if(VisitCard1==null)
                com.Parameters.AddWithValue("@VisitCard1", Convert.ToByte(VisitCard1));
            else
                com.Parameters.AddWithValue("@VisitCard1", VisitCard1);

I Used "If" and "Else" for saving "Null" Value, when user not changed default photo.

Null Data saved as "0x00" in SQL.

When I want show data, i want know that the Data in SQL is Null or not, if is Null, do something, and if not, do something !

But i can't compare Data of SQL with Null value! and when i am using

if(cscompanies.Logo1==Null)

result always is (False) [that mean its not Null, Even when it Saved as Null (0x00)

Zohar Peled · Accepted Answer · 2017-02-11 12:45:25Z

1

Don't confuse c# null with sql server null. They are different things.

Instead of saving c# null in the database, save DBNull.Value:

if(VisitCard1==null)
    com.Parameters.Add("@VisitCard1", SqlDbType.VarBinary, -1).Value = DBNull.Value;
else
   com.Parameters.Add("@VisitCard1", SqlDbType.VarBinary, -1).Value = VisitCard1;

edited Feb 11, 2017 at 12:45

answered Feb 11, 2017 at 9:13

Zohar Peled

82.9k11 gold badges80 silver badges134 bronze badges

Sign up to request clarification or add additional context in comments.

14 Comments

Vesal Parsi Over a year ago

I Used (DBNull.value) insted of (Null) but i meet this error (( Implicit conversion from data type nvarchar to varbinary(max) is not allowed. Use the CONVERT function to run this query.))

Vesal Parsi Over a year ago

Thanks 4 Ur Answer. Ur code was good 4 Null Value and solved my Problem <3 But when i used Ur code 4 saving Photo , when i wanted to show, i meet this Error ((Buffer cannot be null.))........ Did U Understand me? :D

Vesal Parsi Over a year ago

This Part: com.Parameters.Add("@VisitCard1", SqlDbType.VarBinary, -1).Value = VisitCard1; but when i saved with my old code --> ((com.Parameters.AddWithValue("@VisitCard2", VisitCard2);)) it it was shown without Error

Zohar Peled Over a year ago

I've edited my answer once again. Added the missing Convert.ToByte.

Vesal Parsi Over a year ago

Im so sory. Ur Previous Cod Was Correct :D --> com.Parameters.Add("@VisitCard1", SqlDbType.VarBinary, -1).Value = VisitCard1;

|

Vesal Parsi · Accepted Answer · 2017-02-13 08:05:14Z

0

For Visit Image i used this plan:

in class :

if ((dt.Rows[0]["visitcard1"]) != DBNull.Value)
                    VisitCard1 = (byte[])dt.Rows[0]["VisitCard1"];
                else
                    VisitCard1 = null;

and in Form:

 if (csCompanies.Catalog5 != null)
                {
                    byte[] Array = csCompanies.Catalog5;
                    MS = new MemoryStream(Array);
                    picCata5.BackgroundImage = Image.FromStream(MS);
                }

answered Feb 13, 2017 at 8:05

Vesal Parsi

33 bronze badges

Collectives™ on Stack Overflow

how compare a binary(max) value saved in sql to know is it null, in C#?

2 Answers 2

14 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

14 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related