Object Reference Not Set To An Instance Of An Object. In C#....How Can I Pass Not Null For Streamreader Object

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here is my code

C#

public string getUrlRespHtml(string url,
                                    Dictionary<string,> headerDict,
                                    string charset,
                                    Dictionary<string,> postDict,
                                    int timeout,
                                    string postDataStr)
    {
        string respHtml = "";

        //HttpWebResponse resp = getUrlResponse(url, headerDict, postDict, timeout);
        HttpWebResponse resp = getUrlResponse(url, headerDict, postDict, timeout, postDataStr);

        //long realRespLen = resp.ContentLength;

        StreamReader sr;
        if ((charset != null) && (charset != ""))
        {
            Encoding htmlEncoding = Encoding.GetEncoding(charset);
            sr = new StreamReader(resp.GetResponseStream(), htmlEncoding);
            
        }
        else
        {
            sr = new StreamReader(resp.GetResponseStream());         //Here I am Getting Run time Error Like "object reference not set to an instance of an object. in c#" 
        }
        respHtml = sr.ReadToEnd();

        return respHtml;
    }

Posted 16-Jan-14 20:30pm

rameshk14

Updated 16-Jan-14 20:34pm

Maarten Kools

v2

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Maarten Kools 17-Jan-14 2:36am

Sounds to me that resp is null. Did you debug your code and stepped through the getUrlResponse method? I would assume that returns null somewhere.

1 solution

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Tomas Takac · Accepted Answer · 2014-01-16T23:49:00

Solution 1

To avoid null reference passed to the StreamReader you need to restructure your code like this.

C#

string respHtml = "";
 
HttpWebResponse resp = getUrlResponse(url, headerDict, postDict, timeout, postDataStr);
if (resp != null)
{
    var respStream = resp.GetResponseStream();

    if (respStream != null)
    {
        using (var sr = String.IsNullOrEmpty(charset)
            ? new StreamReader(respStream)
            : new StreamReader(respStream, Encoding.GetEncoding(charset)))
        {
            respHtml = sr.ReadToEnd();
        }
                
    }
}
 
return respHtml;

Posted 16-Jan-14 23:49pm

Tomas Takac

Comments

rameshk14 17-Jan-14 5:58am

thank you for your reply, you said that change my code as follows....

string respHtml = "";

HttpWebResponse resp = getUrlResponse(url, headerDict, postDict, timeout, postDataStr);
if (resp != null)
{
var respStream = resp.GetResponseStream();

if (respStream != null)
{
using (var sr = String.IsNullOrEmpty(charset)
? new StreamReader(respStream)
: new StreamReader(respStream, Encoding.GetEncoding(charset)))
{
respHtml = sr.ReadToEnd();
}

}
}

return respHtml;

after changing my code as above i am getting the same error at as Follows.....

private void parseSinglePageHtml(string singlePageGoogleHtml)
{
//

Type-2 Diabetes an Autoimmune Disease? - Hemoblogin - School ...

HtmlAgilityPack.HtmlDocument htmlDoc = crifanLib.htmlToHtmlDoc(singlePageGoogleHtml);
HtmlNode rootHtmlNode = htmlDoc.DocumentNode;
HtmlNodeCollection h3aHtmlNodes = rootHtmlNode.SelectNodes("//h3[@class='r']/a");
foreach (HtmlNode h3aNode in h3aHtmlNodes) //Here is an error
{
if (needContinueSearch)
{
searchItemInfo singleItemInfo = new searchItemInfo();

//InnerHtml
//"Losing weight and belly fat improves sleep - Harvard Health ..."
//InnerText:
//"Losing weight and belly fat improves sleep - Harvard Health ..."
string undecodedTitle = h3aNode.InnerText;
//singleItemInfo.title = HttpUtility.HtmlDecode(undecodedTitle);

singleItemInfo.url = h3aNode.Attributes["href"].Value;

processEachSearchItem(singleItemInfo);
}
else
{
break;
}
}

}

even if i try for any changes in this code i am getting same error some where else

please try to help me....

Richard MacCutchan 17-Jan-14 6:03am

You need to add proper error checking in your program, and use your debugger to find out where it fails. It is no use making a request in your code and just assuming that you will get a valid response. You need to check each response/result and take appropriate action when it fails.

rameshk14 17-Jan-14 6:24am

thank you just now the problem get solved...