Getting NullReferenceException don't know why

Question

I wasn't the one who coded this line of code, and I can't gt to understand whoever did it, why did this way on this line: res.Data.Find(itm => itm.Meta.ID.ToUpper() == i["MetaDataID"].ToString().ToUpper()).Value[i["LocaleID"].ToString()] = i["Value"].ToString(); And this line gives me a NullReferenceException. How can I get around it?

public static void LoadData(Value.Item _res)
    {
        DataTable Res = Connector.Run("SELECT * FROM Data WHERE ItemID='" + _res.ID + "'");

        if (Res.Rows.Count != 0)
        {
            foreach (DataRow i in Res.Rows)
            {
                try
                {
                    _res.Data.Find(itm => itm.Meta.ID.ToUpper() == i["MetaDataID"].ToString().ToUpper()).Value[i["LocaleID"].ToString()] = i["Value"].ToString();
                }
                catch (Exception)
                {
                    _res.Data.Add(new Value.Data(
                                      i["ID"].ToString(),
                                      i["Value"].ToString(),
                                      i["LocaleID"].ToString(),
                                      i["MetaDataID"].ToString()
                                      ));
                }
            }
        }
    }

Thx a lot guys!!! Here is my working solution which hrows no Exceptions anymore!

 public static void LoadData(Value.Item _res)
    {
        DataTable Res = Connector.Run("SELECT * FROM Data WHERE ItemID='" + _res.ID + "'");

        if (Res.Rows.Count != 0)
        {
            foreach (DataRow i in Res.Rows)
            {
                bool _flagged = false;

                var _result = _res.Data.Find(itm => itm.Meta.ID.ToUpper() == i["MetaDataID"].ToString().ToUpper());

                if(_result != null && i["LocaleID"] != null)
                {
                    if (i["Value"] == null || i["LocaleID"] == null || i["MetaDataID"] == null)
                        _flagged = true;

                }
                else
                {
                    _flagged = true;
                }


                if (_flagged)
                {
                    _res.Data.Add(new Value.Data(
                                      i["ID"].ToString(),
                                      i["Value"].ToString(),
                                      i["LocaleID"].ToString(),
                                      i["MetaDataID"].ToString()
                                      ));
                }

                //try
                //{
                //    _res.Data.Find(itm => itm.Meta.ID.ToUpper() == i["MetaDataID"].ToString().ToUpper()).Value[i["LocaleID"].ToString()] = i["Value"].ToString();
                //}
                //catch (Exception)
                //{
                //    _res.Data.Add(new Value.Data(
                //                      i["ID"].ToString(),
                //                      i["Value"].ToString(),
                //                      i["LocaleID"].ToString(),
                //                      i["MetaDataID"].ToString()
                //                      ));
                //}
            }
        }
    }

By the way, you do know that it is more efficient to use string.Compare() rather than ToUpper() on both sides of a string? — Rowland Shaw
– Rowland Shaw, Commented Nov 24, 2011 at 16:42
hm i didn't know it was... I will replace. Gotta do this on other codes too but thkx a lot for the tip!!! — ShadowG
– ShadowG, Commented Nov 24, 2011 at 18:36

Rowland Shaw · Accepted Answer · 2011-11-24 12:48:46Z

2

Impossible to answer accurately without having the code under the debugger, however what is certain is that at least one of the following has a value of null:

_res.Data
itm.Meta
itm.Meta.ID
i["MetaDataID"]
i["LocaleID"]
i["Value"]

answered Nov 24, 2011 at 12:48

Rowland Shaw

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Andras Zoltan · Accepted Answer · 2011-11-24 12:42:04Z

2

Old-skool debugging:

Break the statement down to it's consituent parts - using local variables. Step-through and find which one is null.

answered Nov 24, 2011 at 12:42

Andras Zoltan

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Comments

bobbyalex · Accepted Answer · 2011-11-24 12:42:38Z

1

Check if one of the following are null:

i["MetaDataID"]
i["LocaleID"]
i["Value"]

answered Nov 24, 2011 at 12:42

bobbyalex

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