编辑一个685个字符的字符串，并将子字符串替换为C＃中的另一个字符串

Question

Browse for a folder containing specific files using a folder dialog...

private void btnBrowse_Click(object sender, EventArgs e)
    {
        DialogResult result = fbdPath.ShowDialog();
        if (result == DialogResult.OK)
        {
            string[] files = Directory.GetFiles(fbdPath.SelectedPath);
            txtPath.Text = fbdPath.SelectedPath;
            MessageBox.Show(txtPath.Text.ToString());
        }
    }

Update the file ...

try
        {
            String path = txtPath.Text;
            DirectoryInfo dir = new DirectoryInfo(path);
            FileInfo[] files = dir.GetFiles();
            foreach( FileInfo file in files)
            {
                StreamReader sReader;
                sReader = File.OpenText(dir + @"\" + file.Name );

                StreamWriter sWriter = new StreamWriter(@"f:\" + file.Name);
                while (sReader.EndOfStream == false)
                {
                    string contents = sReader.ReadLine();

                    String Flag = contents.Substring(655, 29);

                    String emBossFName = contents.Substring(41, 40);
                    String emBossLName = contents.Substring(121, 40);

                    String emBossFullName = emBossFName.Trim() + " " + emBossLName.Trim();

                    String newString = emBossFullName;

                    sWriter.WriteLine(contents.Replace(Flag, newString));
                }
                sWriter.Close();
                sReader.Close();
            }
        }
        catch (IOException ex)
        {
            MessageBox.Show(ex.Message.ToString());
        }
    }

I need to replace the 655th position of a string which is of 29 Characters(combination of first & last name of a person seperated by a whitespace), but the problem is the how to maintain fix length of a string which is of 685 characters long?

Answer 1

Just take your final string and call Remove

"...".Remove(684);

And, if you are concerned with it not being long enough, you could first use PadRight

Answer 2

I think that you should make newString exactlly 29 characters long:

if (newString.Length > 29) newString = newString.Substring(0, 29);
if (newString.Length < 29) newString = newString.PadRight(29);

This code trims string if it is longer than 29 charaters or pads right side with spaces if string is shorter than 29 characters.

Answer 3

You can use StringBuilder class.

Ex: replace defg with 1234

StringBuilder sb = new StringBuilder( "abcdefghi");
var newstr = sb.Remove(3, 4).Insert(3, "1234").ToString();