Streamreader

matthew king

Sir /Ma'am,
I'm trying to use streamreader to query a .txt file and change a specific line based on a user input. If the line does not exist, I'm trying to append the data to the bottom of the .txt file. So, the user inputs the data into textbox3 and pushes a button. Upon pushing the button, the code will search c:\test.txt to look for a line beginning with the word entered into textbox3. If it finds it, it simply overrides that line with the value the user entered into textbox2. If the current code doesn't find a line beginning with the word entered into textbox3, it copies the entire .txt file and appends it to the bottom of test.txt. However, as stated above, I just want that one line appended to the buttom, not the entire file. As always, thank you for your assistance!
        private void button3_Click(object sender, EventArgs e)
        {
            StringBuilder sb = new StringBuilder();
            string line = string.Empty;
            // path of the file
            using (StreamReader fs = new StreamReader(@"C:\test.txt", true))
            {
                // checks until end of file
                while ((line = fs.ReadLine()) != null)
                {
                    // This will serch a txt file for the word payload
                    if (line.StartsWith(textBox3.Text))
                        //This will override the sentence....
                        sb.AppendLine(textBox3.Text + ", " + textBox2.Text);
                    else
                        sb.AppendLine(line);
                }
            }
            // path of file that you want to write,
            // and whether you want it to append to the file or not
            // I chose not to append.
            using (StreamWriter sw = new StreamWriter(@"C:\test.txt", true))
            {
                sw.Write(sb.ToString());
            }
        }
    }
}

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Kirtan Patel17y ago
@Arun

Writing in Word File is Not same as Writing in TextFile .

you need to use Office Libraries to Write In A Word File :)

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Arun17y ago
Im trying to do the same using a word file. but getting junk characters. Please guide me
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Danatas Gervi17y ago

I can guess, what is misunderstanding of author.

He probably forgot about NTFS file system. It seems simple – to add some bytes to real disk, but what to do, if the file is fragmented? Or pervious block is not full yet?

Questions…

:-)

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Roei Bar17y ago

here is the fixed code:

   private void button3_Click(object sender, EventArgs e)
        {
	   stringBuilder
           // path of the file
           // Open the file to read from.
           string[] readText = File.ReadAllLines(path);

           //Run on the TextCollection and look for the Text
		
           foreach(string _line in readText)
	   {
		// This will serch a txt file for the word payload
                    if (_line.StartsWith(textBox3.Text))
                        //This will override the sentence....
                        _line = textBox3.Text + ", " + textBox2.Text;
                  
           }

	   
            // and now we will write the file back

	   if (File.Exists(path))
           {
            File.Delete(path);
           }

            File.WriteAllLines(path, readText);
          }

Kirtan Patel17y ago
Dear Friend,

Here is Complete Code to accomplish task according to you described in above post :)

dont forget to mark "Do you like this answer" if my answer helped you :)

private void button1_Click(object sender, EventArgs e)
        {
            string Path = @"E:\Test.txt";
            string SearchText = textBox1.Text.Trim();
            string ReplaceMentString = textBox2.Text.Trim();
            string[] Lines = File.ReadAllLines(Path);
            bool FoundString = false ;

            for (int i = 0; i <= Lines.Length - 1; i++)
            {
                if (Lines[i].StartsWith(SearchText) == true)
                {
                    //Replace the content With Replace ment String
                    Lines[i] = ReplaceMentString;
                    FoundString = true;
                    break;
                }
                i++;
            }

            if (FoundString == false)
            {
                //Append The Line to End of File
                StreamWriter sw = new StreamWriter(Path,true);
                sw.WriteLine(textBox2.Text.Trim());
                sw.Close();
            }
            else
            {
                //Write data back with Replaced String In File
                foreach(string line in Lines)
                {
                    StreamWriter sw = new StreamWriter(Path);
                    sw.WriteLine(line);
                }
            }
        }

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Serban Cosmin17y ago
Hello, The issue is with calling StreamWriter. If the second argument is true, your text is appended to the end of the file. Hence, change that to false to overwrite the file: using (StreamWriter sw = new StreamWriter(@"C:\test.txt", false)).
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