How to check if string is null in c#.net

Question

I am reading text file in c#.net at the end one line is completely null but in foreach c# can not detect null string so It gets error

string[] lines = System.IO.File.ReadAllLines(dir);
List<KeyValuePair<int, DateTime>> items = new List<KeyValuePair<int, DateTime>>();
List<KeyValuePair<int, DateTime>> lst = new List<KeyValuePair<int, DateTime>>();
foreach (string line in lines)
{
    if (line!=string.Empty)
    {
        l = line.Split('\t');
        l[0] = l[0].Trim();
        PersianCalendar persCal = new PersianCalendar();
        SqlConnection sqlconn = new SqlConnection(DBsetting.Connstring);
        SqlCommand sqlda = new SqlCommand("InsertReadd", sqlconn);
        sqlda.CommandType = CommandType.StoredProcedure;
        sqlda.Parameters.AddWithValue("@date", l[1]);
        sqlda.Parameters.AddWithValue("@IDp", l[0]);
        sqlda.Parameters.AddWithValue("@day", GetDayOfWeek(GetPerDate(l[1])));
        sqlda.Parameters.AddWithValue("@nobatkari", "");
        sqlda.Connection.Open();
        sqlda.ExecuteNonQuery();
        sqlda.Connection.Close();
    }
}
RefGrid();

are you looking for `String.IsNullOrEmpty` – sujith karivelil Nov 23 '16 at 08:03 — sujith karivelil, Nov 23 '16 at 08:03
You should include what error you actually get. – Sayse Nov 23 '16 at 08:05 — Sayse, Nov 23 '16 at 08:05
`string.IsNullOrWhiteSpace` is a good choice – Ankit Nov 23 '16 at 08:13 — Ankit, Nov 23 '16 at 08:13

Noxious Reptile · Answer 1 · 2016-11-23T12:27:58.837

2

if(!String.IsNullOrEmpty(line))

just do this and it works

It checks for Null and Empty. This is the used everywhere for this functionality in C#.

EDIT: You can use the following for checking strings which contains whitespaces.

if(!String.IsNullOrWhiteSpace(line))

edited Nov 23 '16 at 12:27

answered Nov 23 '16 at 08:07

Noxious Reptile

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I test it .it doesnot work – javad Nov 23 '16 at 09:17
@javad please show the error u get – Noxious Reptile Nov 23 '16 at 09:18
I get no error but when line is empty it passes from if clause – javad Nov 23 '16 at 12:13
@javad I guess the line is full of Whitespaces. Can you confirm. Please give a clear idea. I will solve it – Noxious Reptile Nov 23 '16 at 12:25
Yes that's true.the line is full of Whitespaces,I am reading lines of a text file with foreach loop – javad Nov 23 '16 at 12:27
@see my updated code. hope It will work for you. – Noxious Reptile Nov 23 '16 at 12:29

Timon Post · Answer 2 · 2016-11-23T08:10:09.190

0

CHECK

change:

 if (line!=string.Empty)

to:

  //check if the sting = null or empty
  if (!String.IsNullOrEmpty(line))
  { 
     //some code 
  }

edited Nov 23 '16 at 08:10

answered Nov 23 '16 at 08:04

Timon Post

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How to check if string is null in c#.net

2 Answers2