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I am getting "object reference error" while putting string.format in stringbuilder. I have below code in C#2.0

public const string PageLinkGoogleMarkup = "<link rel=\"alternate\" hreflang=\"{0}\" href=\"{1}www.mysite.com{2}{3}\" />\r\n";

Now when I am adding this to HtmlTextWriter it is working fine, as below:

HtmlTextWriter writer (Object);
writer.write(string.format(PageLinkGoogleMarkup,str[1],header,links,querystr)); //This works perfect

And when I tries to add this above code to StringBuilder instead of HtmlTextWriter it gives error:

As there is big loop so I decided to go with appending everything to StringBuilder first and at last rendering using writer.Write (Whole html in a bunch), please below code

StringBuilder sb = new StringBuilder();
sb.Append(string.format(PageLinkGoogleMarkup,str[1],header,links,querystr)); //here i get object reference error

writer.Write(sb.ToString());

Please suggest!!

Thanks.

share|improve this question
Do you mean "Object reference not set to an instance of an object"? – Chris Shain May 23 '12 at 14:40
Yes, "Object reference not set to an instance of an object" – Manoj Singh May 23 '12 at 14:45

1 Answer

up vote 0 down vote accepted

One of the following variables is null when you are using it in the StringBuilder code (but was not null when you used it in the working code):

str (or the item in index [1])
header
links
querystr

Use the debugger to figure out which one is null, fix that, and the code should work fine.

share|improve this answer
I don't think that is the issue as it works perfect with writer.write..any ideas – Manoj Singh May 23 '12 at 14:51
You have not provided enough code to be entirely sure which one is null, but I'm fairly sure that this is the problem. – Chris Shain May 23 '12 at 14:55
see onething "querystr" can be empty but not null as it if current page has querystring then only this variable will have value , does that can cause issue – Manoj Singh May 23 '12 at 14:59
Problem Resolved actually StringBuilder object was getting in NULL – Manoj Singh May 24 '12 at 5:13

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