Replace first occurence of a string in c#

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The following is the code for replacing fist occurrence of a string in a file.

public static string ReplaceFirstOccurrance(string original, string oldValue, string newValue)
{
    if (String.IsNullOrEmpty(original))
        return String.Empty;
    if (String.IsNullOrEmpty(oldValue))
        return original;
    if (String.IsNullOrEmpty(newValue))
        newValue = String.Empty;
    int loc = original.IndexOf(oldValue);
    if(loc==-1)
       return original;
    return original.Remove(loc, oldValue.Length).Insert(loc, newValue);
}

If the string that I want to replace is the last line of the file then it is not getting replaced.Any idea why this is happening?

This is the code from where I am calling the function

 private void Transform_Click(object sender, EventArgs e)
        {
                      FileStream fread = new FileStream(despath, FileMode.Open);
                            StreamReader sfread = new StreamReader(fread);
                            string txt = sfread.ReadToEnd();
                            fread.Close();
                            
                            string actual ="This is actual Sample";
                       
                            string replace = "This is replaced line"+count;
                       
                            string replaceVariable = ReplaceFirstOccurrance(txt, actual, replace);
                         
                            FileStream filewrite = new FileStream(despath, FileMode.Create);
                            StreamWriter filew = new StreamWriter(filewrite);

                            filew.Write(replaceVariable);

                            filew.Close();
                            filewrite.Close();
                            count++;
}

If "This is actual sample" is the last line in the file,it is not getting replaced.

Posted 3-Oct-12 21:04pm

DhanashreeRamya

Updated 3-Oct-12 23:37pm

v2

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Comments

Rockstar_ 4-Oct-12 3:10am

Are you reading the file line by line or using function readtoend(). make sure that it is reading the last line or not..

DhanashreeRamya 4-Oct-12 3:12am

I am reading it line by line.

Guirec 4-Oct-12 3:35am

Whether your function is not called at all for the last line, whether your "oldValue" is not in the line... Your function should work fine. Problem must be external.

n.podbielski 4-Oct-12 6:23am

What is count variable? A field?

2 solutions

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

sjelen · Answer 1 · 2012-10-04T00:11:00

And what is wrong with using string.Replace()?

C#

if (original==null) return string.Empty
else return original.Replace(oldValue, newValue);

Also, you are not reading file line by line, you read it whole at once into one string. If you have "This is actual sample" in 2 or more places, only first will be replaced.

Reading and replaceing line by line:

C#

private void Transform_Click(object sender, EventArgs e)
{
    FileStream fread = new FileStream(despath, FileMode.Open);
    StreamReader sfread = new StreamReader(fread);
    FileStream filewrite = new FileStream(despath, FileMode.Create);
    StreamWriter filew = new StreamWriter(filewrite);

    while (!sfread.EndOfStream)
    {
        string line = sfread.ReadLine();
        
        string replaceVariable = ReplaceFirstOccurrance(line, 
            "This is actual Sample", 
            "This is replaced line"+count.ToString());
                    
        filew.Write(replaceVariable);
count++;
    }    
    filew.Close();
    filewrite.Close();
    
fread.Close();
}

psychic6000 · Answer 2 · 2012-10-03T22:41:00

Solution 2

because it deletes the position, insert() doesnt find any loc
try this instead for your line return "original.Remove(loc, oldValue.Length).Insert(loc, newValue);"

C#

string temp = orignal.Substring(0, orignal.IndexOf(oldv));
string temp2 = orignal.Substring(orignal.IndexOf(oldv) + oldv.Length);
return temp + newv + temp2;

Posted 3-Oct-12 22:41pm

psychic6000

Comments

DhanashreeRamya 4-Oct-12 4:59am

this still doesn't replace the last line of the file.

Mohd. Mukhtar 4-Oct-12 5:02am

Could you please post the code from where you calling ReplaceFirstOccurrance method?

Replace first occurence of a string in c#

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Replace first occurence of a string in c#

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