Formatting Multiline Textbox content

When you display multiple lines of data from the database you loose the spacing or formatting between multiple lines of data. Also in some applications like Forums, where users can post HTML content directly which can lead to some serious problems, Someone can post a link to some malicious coded page and all the users can become easy targets which can cause some serious security implications.

There is a common solution to both the above problems, you have to parse the Text content from the Database into respective HTML tags.

1) Formatting Solution: In HTML denotes a extra white space. So every 2 white spaces should be substituted by a single white space and .
Also every line terminator should be replaced by the break tag
, which will result in the next character starting for a new line.

2) HTML Content: The solution to this is a bit tricky, in HTML every valid tag is contained within the <> brackets. So to make all the HTML tags in your post invalid just change the <> tags to their HTML counter parts < and > respectively. Also one other formatting change to be made is that the double quotation mark " has to be changed into its HTML equivalent "


Code

1) ParseText method :- The method to convert Text into HTMLpublic string parsetext(string text, bool allow)
{
//Create a StringBuilder(using System.Text namesapace) object from the string input
//parameter
StringBuilder sb = new StringBuilder(text) ;
//Replace all double white spaces with a single white space
//and
sb.Replace(" "," ");
//Check if HTML tags are not allowed
if(!allow)
{
//Convert the brackets into HTML equivalents
sb.Replace("<","<") ; sb.Replace(">",">") ;
//Convert the double quote
sb.Replace("\"",""");
}
//Create a StringReader from the processed string of
//the StringBuilder
StringReader sr = new StringReader(sb.ToString());
StringWriter sw = new StringWriter();
//Loop while next character exists
while(sr.Peek()>-1)
{
//Read a line from the string and store it to a temp
//variable
string temp = sr.ReadLine();
//write the string with the HTML break tag
//Note here write method writes to a Internal StringBuilder
//object created automatically
sw.Write(temp+"
") ;
}
//Return the final processed text
return sw.GetStringBuilder().ToString();
}


2) textparser.aspx - A sample consumer for the Text to HTML parser
private void Post_Text(object sender, EventArgs e)
{
//Check if there is some text inside the TextBox
if(mess.Text!="")
{
//Check if option to Parse Text is selected
if(parse.Checked)
{
//Check if option to convert HTML tags to text is selected
if(htmlpost.Checked)
{
//Call the parsetext method
//Pass the text content from the textbox and false so that
//HTML tags do not get converted to text
postmess.Text=parsetext(mess.Text,false) ;
}
else
{
//Call the parsetext method
//Pass the text content from the textbox and true so that
//HTML tags get converted to text
postmess.Text=parsetext(mess.Text,true) ;
}
}
else
{
//Just post the text without any parsing
postmess.Text=mess.Text ;
}
}
}

//Method to parse Text into HTML
public string parsetext(string text, bool allow)
{
//Create a StringBuilder object from the string input
//parameter
StringBuilder sb = new StringBuilder(text) ;
//Replace all double white spaces with a single white space
//and
sb.Replace(" "," ");
//Check if HTML tags are not allowed
if(!allow)
{
//Convert the brackets into HTML equivalents
sb.Replace("<","<") ; sb.Replace(">",">") ;
//Convert the double quote
sb.Replace("\"",""");
}
//Create a StringReader from the processed string of
//the StringBuilder object
StringReader sr = new StringReader(sb.ToString());
StringWriter sw = new StringWriter();
//Loop while next character exists
while(sr.Peek()>-1)
{
//Read a line from the string and store it to a temp
//variable
string temp = sr.ReadLine();
//write the string with the HTML break tag
//Note here write method writes to a Internal StringBuilder
//object created automatically
sw.Write(temp+"
") ;
}
//Return the final processed text
return sw.GetStringBuilder().ToString();
}