conversion of binary file to a text file

If you are dealing with simple data types, then you can use BinaryReader and StreamWriter classes.
For example:

using (StreamWriter writer = new StreamWriter(textFileName))
{
    using (BinaryReader reader = new BinaryReader(
        File.Open(binaryFileName, FileMode.Open)))
    {
        //reads an int
        int myInt = reader.ReadInt32();
        //writes it
        writer.WriteLine(myInt);
        //reads a float
        float myFloat = reader.ReadSingle();
        //writes it
        writer.WriteLine(myFloat);
        ...
    }
}

But binary files can contain any kind of data. So it is up to you to read the data properly...