How do I load a Null blob

Question

1.00/5 (1 vote)

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Windows Forms
VS2013

I have a profile form and a profile edit form

on the profile form when it loads the image should be from the properties if the field in the db is NULL which at account creation it is.

However when it loads I get a error blow is the code for the form load

C#

mcon.Open();
          label9.Text = label10.Text;
           using (MySqlCommand cmd = mcon.CreateCommand())
           {
               cmd.CommandText = "SELECT * FROM users WHERE username='" + label10.Text + "'";
               using (MySqlDataReader rd = cmd.ExecuteReader())
               {
                   while (rd.Read())
                   {
                       lbluser.Text = rd.GetString("username");
                       lblname.Text = rd.GetString("full_name");
                       lblage.Text = rd.GetString("age");
                       lblcountry.Text = rd.GetString("country");
                       lblmartialstatus.Text = rd.GetString("martial_status");
                       lblgender.Text = rd.GetString("gender");
                       lblhobbies.Text = rd.GetString("hobbies");

                    byte[] imgg = (byte[])(rd["profile_pic"]);


                       if (imgg == null)
                       {
                           profilepic.Image = Properties.Resources._default;
                           path.Text = "Default Image";

                       }

                       else
                       {
                           MemoryStream mstream = new MemoryStream(imgg);
                           profilepic.Image = System.Drawing.Image.FromStream(mstream);
                       }




                   }

               }
           }

the line of code

C#

byte[] imgg = (byte[])(rd["profile_pic"]);

I get the error on and this happens the same way on the profile edit

If anyone has any ideas it would be great

Posted 11-Oct-15 12:44pm

Member 11002137

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Comments

Dave Kreskowiak 11-Oct-15 19:41pm

...and the error message would be ......?? Hint: IMPORTANT!

[no name] 11-Oct-15 19:44pm

An unhandled exception of type System.InvalidCastException occurred in client.exe
Unable to cast object of type system.DBNULL to type System.Byte

2 solutions

Solution 2

I got it working

I change my code to

C#

if (rd["profile_pic"] == DBNull.Value)
                   {
                       profilepic.Image = Properties.Resources._default;
                       path.Text = "Default Image";

                   }

                      else
                      {
                          byte[] imgg = (byte[])(rd["profile_pic"]);
                       MemoryStream mstream = new MemoryStream(imgg);
                          profilepic.Image = System.Drawing.Image.FromStream(mstream);
                      }

Posted 11-Oct-15 14:17pm

Member 11002137

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Dave Kreskowiak · Accepted Answer · 2015-10-11T13:48:00

Solution 1

Well, then it's pretty obvious. A C# null is not the same as a DbNull coming from the database. You cannot cast that to anything in C#. You have to check to see if the value is DbNull BEFORE you attempt to convert the value to an array of bytes.

Posted 11-Oct-15 13:48pm

Dave Kreskowiak

Comments

Dave Kreskowiak 11-Oct-15 20:17pm

if (rd["profile_pic"] == DbNull)

How do I load a Null blob

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How do I load a Null blob

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