How to Use iterator to traverse File Information

1. iterate the row of the file
Copy codeThe Code is as follows:
Public static IEnumerable <string> ReadLines (string fileName)
{
Using (TextReader reader = File. OpenText (fileName ))
{
String line;
If (line = reader. ReadLine ())! = Null)
{
Yield return line;
}
}
}
Static void Main ()
{
Foreach (string line in Iterator. ReadLines (""))
{
Console. WriteLine (line );
}
}

2. Use the iterator and predicate to filter rows in the file.
Copy codeThe Code is as follows:
Public static IEnumerable <T> where <T> (IEnumerable <T> source, Predicate <T> predicate)
{
If (source = null | predicate = null)
{
Throw new ArgumentNullException ();
}
Return WhereImplemeter (source, predicate );
}
Private static IEnumerable <T> WhereImplemeter <T> (IEnumerable <T> source, Predicate <T> predicate)
{
Foreach (T item in source)
{
If (predicate (item ))
{
Yield return item;
}
}
}
Static void Main ()
{
IEnumerable <string> lines = File. ReadAllLines (@ "your file name ");
Predicate <string> predicate = delegate (string line)
{
Return line. StartsWith ("using ");
};
Foreach (string str in where (lines, predicate ))
{
Console. WriteLine (str );
}

}