How to Handle huge string Data in a C# code.

Why do you need to hard-wire the strings in you program? Cannot you read them from a 'configuration' file?
:)

I think you don't need that StringBuilder at all!

The following code:

StringBuilder UptoMain = new StringBuilder();
StreamWriter file = new StreamWriter(@"c:\temp.txt", false);
UptoMain.AppendLine(@"Here there is lots and lots of text which makes the code look very ugly and and messy to hande");
file.WriteLine(UptoMain);

can be reduced to:

StreamWriter file = new StreamWriter(@"c:\temp.txt", false);
string s = @"Here there is lots and lots of text which makes the code look very ugly and and messy to hande";
file.WriteLine(s);

This does not sort your problem with the long string though... If you really need to keep the string in code, all you can do is to move the string constant somewhere else. You can write something like:

private const string MyString = @"Here there is lots and lots of text which makes the code look very ugly and and messy to hande";

...and then use MyString in the code later. This will make your code more readable, since you can move the string constant declaration anywhere you like, even to a separate file.

You might make it a bit moduler.

public void WriteFile(string filename, string text)
{
    using(StreamWriter file = new StreamWriter(filename, false))
    {
         file.WriteLine(text);
    }

}

From your application you call this method using :

StringBuilder UptoMain = new StringBuilder();
UptoMain.AppendLine(....);
this.WriteFile(@"c:\temp.txt", UptoMain.ToString());

Using is essential as it disposes the object after you are done writing.
:thumbsup: