c# linq select new class Error : Object reference not set to an instance of an object

Question

i want to bind gridview with my custom entity whitch i populate from data base but i get error Object reference not set to an instance of an object i know the error is from my gridlink class when select new and want to set to link property in this line : link = { linkName = "tyr", linkSrc = "ytr" }, because when i earase it the error stop and gridview bind thanks

  public class gridcolumns
{

    public decimal cost { get; set; }
    public Int32 count { get; set; }
    public gridlink link { get; set; }

    public gridcolumns()
    {

        // TODO: Complete member initialization
    }
}

public class gridlink
{
    public string linkName { get; set; }
    public string linkSrc { get; set; }

    public gridlink()
    {

    }
}
 protected void Page_Load(object sender, EventArgs e)
{
    Data281DataContextDataContext conx = new Data281DataContextDataContext();
    List<tbl_2_CheckReqNo_NotValid> allresult = conx.tbl_2_CheckReqNo_NotValids.ToList();
    gridcolumns lastMantWithDate = new gridcolumns();
    if (Request.QueryString.Count == 0)
    {
        var lastMantWithDaste = from pe in allresult //where allresult != null
                                orderby Convert.ToDecimal(pe.mandeh) descending
                                group pe by pe.mant into grouped
                                where grouped != null
                                select new gridcolumns
                                {
                                    link = { linkName = "tyr", linkSrc = "ytr" },
                                    cost = grouped.Sum(g => Convert.ToDecimal(g.mandeh)),
                                    count = grouped.Count(),

                                };

        GrdOstan.DataSource = lastMantWithDaste;
        GrdOstan.DataBind();
    }

possible duplicate of [What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net) — , Aug 29 '12 at 07:34
are you shure, that this even compiles? i believe that `link = { linkName = "tyr", linkSrc = "ytr" },` should throw an error ... — , Aug 29 '12 at 07:37

score 4 · Accepted Answer · answered Aug 29 '12 at 07:34

You should be instantiating a gridlink like this:

link = new gridlink { linkName = "tyr", linkSrc = "ytr" },

Consider that for each item your query produces you create a gridcolumns object. The link property of that object is initially null; you should set it to new gridlink before trying to use it at all.

score 3 · Answer 2 · answered Aug 29 '12 at 07:34

3

You probably need

link = new gridLink { linkName = "tyr", linkSrc = "ytr" }

instead of

link = { linkName = "tyr", linkSrc = "ytr" }

answered Aug 29 '12 at 07:34

Graham Clark

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score 1 · Answer 3 · answered Aug 29 '12 at 07:36

Replace this:

select new gridcolumns
           {
           link = { linkName = "tyr", linkSrc = "ytr" },

With:

select new gridcolumns
           {
           link = new gridlink  { linkName = "tyr", linkSrc = "ytr" },

You need to instantiate a new object of type gridLink using the new keyword

score 0 · Answer 4 · edited Aug 29 '12 at 16:30

In your line:

link = { linkName = "tyr", linkSrc = "ytr" }

You need "new gridlink", like this:

link = new gridlink { linkName = "tyr", linkSrc = "ytr" }

Personally, I think it's unfortunate that your code compiled. If I tried:

List<gridlink> links = new List<gridlink>();
links.Add({ linkName = "tyr", linkSrc = "ytr" });

I would correctly get a bevy of syntax errors.

Adding new gridlink should resolve this problem.

c# linq select new class Error : Object reference not set to an instance of an object

4 Answers4