CODEWITHSUNDEEP
c#asp.net
Jeyavel
Jeyavel

Reputation: 3030

How to Handle the Hashtable null value?

I have a problem while checking a hashtable value. In the code below I am storing 60 values in the hashtable "hash". One of the values is (or can be) Null. I am checking each entry against its corresponding entry in hashtable "hash1", to see if they match each other. If they don't match I want to check if the value in "hash" is Null, but I can't catch it - it's falling through the 'else' part). How can I overcome this problem?

if (hash[j].ToString() == "")
{
    NotAnswerQuestionCount++;
}

My Code:

int ctAnsCount=0, flAnsCount=0,NotAnswerQuestionCount=0;
SqlDataAdapter sda = 
    new SqlDataAdapter("select quesno,[Key] from Answerkey" ,con);
DataSet ds = new DataSet();
sda.Fill(ds);

Hashtable hash = new Hashtable();

for (int i = 0; i < 60; i++)
{
    hash[i+1] = ResultsListBox.Items[i].ToString();
}

Hashtable hash1 = new Hashtable();

for (int i = 0; i < 60; i++)
{
    hash1[i+1] = ds.Tables[0].Rows[i][1].ToString();
}

for (int j = 1; j <=60; j++)
{
    if (hash[j].ToString() != hash1[j].ToString())
    {
        if (hash[j].ToString() == "")
        {
            NotAnswerQuestionCount++;
        }
        //else


        flAnsCount++;
    }
    else
    {           
        ctAnsCount++;    
    }
}

Upvotes: 1

Views: 11637

Answers (5)

Greg B
Greg B

Reputation: 14898

You could try using if(string.IsNullOrEmpty(hash1[i])) or check for null prior to calling ToString().

if (hash[i] != null &&
    hash[i].ToString() == "")
    {
      ...

Upvotes: 1

Kwang-Chun Kang
Kwang-Chun Kang

Reputation: 351

If you want to check whether a Hash Object is null or size is zero.

I think you can do like this

if (hash!= null || hash.Keys.Count==0) { blah }

Thank you.

Upvotes: 0

w33z33
w33z33

Reputation: 378

From C# 6 and onwards you can use the Null-conditional operator ?.

if (hash[i]?.ToString() == "") { ...

Upvotes: 0

gkrogers
gkrogers

Reputation: 8356

I don't think you mean null, I think you mean empty. You're checking the contents of 'hash', which looks like it is filled from a ListBox, but AFAIK a ListBox item can't be null. Also, you're checking to see if it matches the empty string ("").

How do you know that you have an empty string in the ListBox? Try Trim-ing the value before you check it (i.e. if (hash[j].ToString().Trim() == "") to catch empty strings as well as strings that only contain whitespace. Alternatively output the contents of each ListBox item to debug, bracketed by a delimiter, to check that you've actually got, like so:

foreach (Object o in ResultsListBox.Items) {
  Debug.WriteLine("'" + o.ToString() + "'");
}

Upvotes: 0

Raj
Raj

Reputation: 1770

Test for hash1[i] != null prior to using ToString().

Upvotes: 1

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