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

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
– sujith karivelil

2016-11-23 08:03:20 +00:00
Commented Nov 23, 2016 at 8:03 — sujith karivelil
– sujith karivelil, Commented Nov 23, 2016 at 8:03
You should include what error you actually get.

Sayse
– Sayse

2016-11-23 08:05:18 +00:00
Commented Nov 23, 2016 at 8:05 — Sayse
– Sayse, Commented Nov 23, 2016 at 8:05
string.IsNullOrWhiteSpace is a good choice

Ankit
– Ankit

2016-11-23 08:13:36 +00:00
Commented Nov 23, 2016 at 8:13 — Ankit
– Ankit, Commented Nov 23, 2016 at 8:13

Noxious Reptile · Accepted Answer · 2016-11-23 12:27:58Z

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, 2016 at 12:27

answered Nov 23, 2016 at 8:07

Noxious Reptile

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6 Comments

javad Over a year ago

I test it .it doesnot work

Noxious Reptile Over a year ago

@javad please show the error u get

javad Over a year ago

I get no error but when line is empty it passes from if clause

Noxious Reptile Over a year ago

@javad I guess the line is full of Whitespaces. Can you confirm. Please give a clear idea. I will solve it

javad Over a year ago

Yes that's true.the line is full of Whitespaces,I am reading lines of a text file with foreach loop

|

Timon Post · Accepted Answer · 2016-11-23 08:10:09Z

0

CHECK

change:

 if (line!=string.Empty)

to:

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

edited Nov 23, 2016 at 8:10

answered Nov 23, 2016 at 8:04

Timon Post

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