Question

The problem occuring on updating only email all other blanks get null . Even if i unchecked allow null in sql server 2008 .my code is-

protected void Updateinfo_Click(object sender, EventArgs e)
{
    string radiogender;
    if (Radiochngmale.Checked == true)
        radiogender = Radiochngmale.Text.ToString();
    else
        radiogender = Radiochngfemale.Text.ToString();
    SqlConnection con = new SqlConnection();
    con.ConnectionString = ConfigurationManager.ConnectionStrings["Con"].ConnectionString;
    con.Open();
    if (con.State == ConnectionState.Open)
    {
        SqlCommand cmd = new SqlCommand();
        Random r = new Random();
        int next = r.Next();
        if (FileUpload2.HasFile)
        {
            string myMap = MapPath("~/").ToLower();
            string ImageName = FileUpload2.PostedFile.FileName;
            sImageFileExtension = ImageName.Substring(ImageName.LastIndexOf(".")).ToLower();
            if (sImageFileExtension == ".gif" || sImageFileExtension == ".png" || sImageFileExtension == ".jpg" || sImageFileExtension == ".jpeg" || sImageFileExtension == ".bmp")
            {
                string ImageSaveURL = myMap + "UserImage/" + next + sImageFileExtension;
                FileUpload2.PostedFile.SaveAs(ImageSaveURL);
            }
            else
                Response.Write("Invalid File");
        }
        cmd.Connection = con; 
        if(chngfname.Text==null)
            chngfname.Text="Select Firstname from Login where Email='"+Session["UserName"]+"'";
        if (chnglastname.Text == null)
            chnglastname.Text = "Select Lastname from Login where Email='" + Session["UserName"] + "'";
        if (chngage.Text == null)
            chngage.Text = "Select age from Login where Email='" + Session["UserName"] + "'";
        if (chngemail.Text == null)
            chngemail.Text = "Select Email from Login where Email='" + Session["UserName"] + "'";
        if (radiogender == null)
            radiogender = "Select gender from Login where Email='" + Session["UserName"] + "'";
        if (chngpassword.Text == null)
            chngpassword.Text = "Select Password from Login where Email='" + Session["UserName"] + "'";
        if ( FileUpload2.HasFile==null)
             sImageFileExtension = "Select profile_pic from Login where Email='" + Session["UserName"] + "'";
        if (chngfname.Text == null)
            chngfname.Text = "Select Firstname from Login where Email='" + Session["UserName"] + "'";
        cmd.CommandText =  "Update Login set FirstName = '"+chngfname.Text+"',LastName='"+chnglastname.Text+"',Email='"+chngemail.Text+"',Password='"+chngpassword.Text+"' ,gender='"+radiogender+"',age='"+chngage.Text+"' , profile_pic='"+ next + sImageFileExtension + "' where Email='"+Session["UserName"]+"'";  
        cmd.CommandType = CommandType.Text; 
        cmd.ExecuteNonQuery();
        }
    }

Why didn’t it is taking the previous values even if i mentioned it to take.Please check it out and sort it out

Answer 1

This is happening because TextBox.Text is never null so your SQL query ends up looking like this:

Update Login 
  set FirstName = '', 
      LastName = '',
where Email = '[e-mail]'

-- etc...

Except for the one or two fields where the data is actually set to something. Here’s probably what you wanted it to look like:

update login
  set FirstName = 'John', 
      LastName = (select Lastname from login where email = '[e-mail]'), 
      etc...
where email = '[e-mail]'

But, there no need for the subqueries. If you want to avoid overwriting values where a value is null or empty string, then you want your SQL to look like the following, use Parameters and set them to DbNull when the textbox is empty.

cmd.Parameters.AddWithValue("@FirstName", (chngfname.Text == String.Empty) ? DbNull.Value : chngfname.Text;

update login
  set FirstName = coalesce(@firstName, FirstName), 
      LastName = coalesce(@LastName, LastName), 
      etc...
where Email = @Email

The other option is select the record first (which I’m sure you’ve already done) and simply use the same value that’s already in the database.

if (chngfname.Text == String.Empty) chngfname.Text = Session["CurrentUserEntity"].FirstName;

Additionally, you need to change this to a parametrized query:

string sql = "update login set FirstName = @firstName, LastName = @lastName, etc... where email = @email;
cmd.Parameters.Add(...);