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How do I replace a part of a line in a text file with user input?

Here's the code.
private void SaveButton_Click(object sender, EventArgs e)
{
string textBoxText = TextBox.Text;
var lines = File.ReadAllLines(#"F:\Bioshock2SP.ini");
foreach(string line in lines)
{
if (line.Contains("VoVolume="))
{
//This is where I get confused.
string settingLine = line;
string replaceline = (line.Replace(line, textBoxText));
File.WriteAllText(#"F:\Bioshock2SP.ini", settingLine);
}
break;
}
MessageBox.Show("Setting saved!");
}
The idea is to replace part of a setting in a Settings.ini file for a game I play, using the user input of a textbox in my form. The user types in a number for example, "1.56" and then hit the Save button to replace the existing line with their input. In this case that setting is the volume.
The application runs completely fine, but after hitting save and going into the settings file my input isn't saved.

There should be a change in the way you save the file.
Save each line of the file as you get it, editing if required.
void SaveButton_Click(object sender, EventArgs e)
{
var textBoxText = TextBox.Text;
var lines = File.ReadAllLines(#"F:\Bioshock2SP.ini");
using (var file = new StreamWriter(#"F:\Bioshock2SP.ini"))
foreach(string line in lines)
{
if (line.Contains("VoVolume="))
file.WriteLine(line.Substring(0, 9) + textBoxText); // Writes something like 'VoVolume=1.56'
else file.WriteLine(line); // No editing required
}
MessageBox.Show("Setting saved!");
}

I think there are a couple of separate issues with your code:
Replace Function
string replaceline = (line.Replace(line, textBoxText));
Replace accepts a string to look for and a string to replace it with. Your first argument is 'line', so it would replace the whole line with the value in textBoxText. I assume you only want to replace a portion of the line with that value. In that case, you need to use something like line.Replace(searchString, textBoxText) where you have previously defined searchString as the text you want to replace. If you don't know what that value is, but there is a pattern, you might want to look into using regular expressions which will let you define a pattern to search and replace.
WriteAllText Function
File.WriteAllText(#"F:\Bioshock2SP.ini", settingLine);
This line will replace the entire contents of BioShock2SP.ini with the value in settingLine. There are two problems here.
One is that settingLine was the saved value before you did the replacement - so it has not included the results of your replace operation. You should use replaceline (assuming it has been correctly modified).
Even if you do that, though, the other is that File.WriteAllText will replace the whole file with the value in settingLine - which is probably not what you want. You'd be better off modifying the line in the array and using File.WriteAllLines to re-output the whole array - assuming the file has multiple lines in it.
The hints above may help you resolve this - to properly answer the question though, I'd need to see a sample of what the file looks like, and the patterns you are trying to replace.

How do I get the Bitmap name when I click the image in datagridview?

I am trying to click on an image in a datagridview and then write its image/file name into a textbox so I can access this from elsewhere.
First I try just a small app to make sure I can make it all work. A Dialog contains the dataviewgrid and I put a bitmap into it as below:
public ChooseFormat()
{
InitializeComponent();
dataGridView1[0,0].Value = new Bitmap(#"C:\a\eggs\grid_app\grid_app\bin\Debug\graphics\1L5HQ60.bmp");
}
Now I click on the image but all the things I have tried I cannot get hold of the file name. The closest I get is below but this returns "System.Drawing.Bitmap" and not the file name. I am sure this must just be a tweak here to make it work but I have tried teh few things I know and nothing is working.
void DataGridView1CellContentClick(object sender, DataGridViewCellEventArgs e)
{
txtbx_choice.Text = dataGridView1[0,0].Value.ToString();
}

Drilling into the cells's data in the debugger doesn't bring up any info on the source of it. Maybe I have overlooked something..
One simple solution is to store the filename in the cell's Tag property:
string fileName = #"C:\a\eggs\grid_app\grid_app\bin\Debug\graphics\1L5HQ60.bmp";
dataGridView1[0,0].Value = new Bitmap(fileName );
dataGridView1[0,0].Tag = fileName ;
Now you can always access it:
string displayedFile = dataGridView1[0, someRow].Tag.ToString();

I have placed a Picture Box on the same form and this how I am displaying the ImageColumn's data (an Image ) in picture box
pictureBox1.Image = (Image)dataGridView1[0, 0].Value;

display a string in textbox

I want to get the data from my serial port and display this data in a textbox. but when i run mu code it displays just one line in the textbox and it gets replaced by the next. but I want the each part of the string under the next one.
private void button1_Click(object sender, EventArgs e)
{
SerialPort serP = new System.IO.Ports.SerialPort("COM3", 9600, System.IO.Ports.Parity.None, 8, System.IO.Ports.StopBits.One);
while (true)
{
serP.Open();
serP.WriteLine("test");
string dataIn = serP.ReadLine();
textBox1.Text = dataIn;
serP.Close();
}
}
this is my code, I hope some one can help me out with this.
Rick

Just concatenate your text:
textBox1.Text += dataIn + Environment.NewLine;
And make sure your textbox is multiline (textBox1.Multiline = true for standart Windows.Forms.TextBox or somethimg similar if it's textbox from some controls library)

I would go with Andy Korneyev's answer. But if you want each part in a new line you could alter his code like below,
textBox1.Text += dataIn + Environment.NewLine;
Also if you want to set the textbox as MultiLine in code behind,
textBox1.TextMode = TextBoxMode.MultiLine;
Note:
I assume you are working with WinForms. If so, you can also use RichTextBox control. It doesn't need to be set has MultiLine.

I agree with Pavan. If you want to use more than one line i would prefer RichtTextBox, too.
Also if you only want to display something, you could use a simple label, too.
I think thats much nicer for a user than to have it in a TextBox, but only if you want to display something without using it in other things.

How do I display default text in EditControls?

What is the easiest way to recreate the effect where a text box displays a certain string (in italics and different font) until the user has clicked into the control and/or written his own text into the field? For an example, look at the "search" box at the top right of SO.
I have tried consuming the Paint event:
private void textEdit1_Paint(object sender, PaintEventArgs e)
{
if (textEdit1.Text.Length == 0 && !textEdit1.Focused)
{
textEdit1.Font = new Font(textEdit1.Font, FontStyle.Italic);
textEdit1.Text = "123";
}
else
{
textEdit1.Font = new Font(textEdit1.Font, FontStyle.Regular);
textEdit1.Text = string.Empty;
}
}
However, that's not working. By default, it shows no text, and if I click into it, I seem to get an infinite loop of setting the text to "123" and string.empty, until I give another control focus.
So, is that approach even the best, and if yes, what's the correct 2nd condition instead of .Focused?

Try the TextEdit.Properties.NullValuePrompt property. This property provides the text displayed grayed out when the editor doesn't have focus, and its edit value is not set to a valid value.

First of all, you shouldn't use the paint event, you should use the FocusChanged event if you want to do it by modifying the text property. However, the simplest method is not to modify the text property, but draw a string on top, like this:
private void textEdit1_Paint(object sender, PaintEventArgs e)
{
if (textEdit1.Text.Length == 0 && !textEdit1.Focused)
{
Font some_font = new Font(...parameters go here...);
Brush some_brush = Brushes.Gray; // Or whatever color you want
PointF some_location = new PointF(5,5); // Where to write the string
e.Graphics.WriteString("some text", some_font, some_brush, some_location);
}
}
So, if there is no text, and text box is not focused, draw this string. There are many overloads of the WriteString function, so you can pick which one you want.

You can use the Enter event. Set Text property to "search" for example. Use your font like others reported. Then catch the Enter event and set the Text property to string.empty.
textedit1.Text = "search";
private void textEdit1_Enter(object sender, EnterEventArgs e)
{
textedit1.text = string.empty;
}
But i think the best practice is the NullValuePrompt.

C# Text box remaining empty

I'm calling a public method from another class. It takes in a List as a parameter, and goes through the list printing out each item into a text field. The problem is the text field is remaining empty!. I've checked that the list is populated by outputing the item to the console before I put it into the text box, and the text is coming up fine there.
The list contains strings, and should output each string to the textfield followed by a semi colon.
This is the method which is being called:
public void fillAttachment(List<string> attachList)
{
for (int i = 0; i < attachList.Count; i++)
{
Console.WriteLine("List: " + attachList[i]);
txtAttach.Text += attachList[i] + ";";
}
}

I would solve it in this way:
foreach(var attach in attachList)
{
Console.WriteLine(attach);
txtAttach.AppendText(string.Format("{0};", attach));
}

Setting the text property on a text box and it not displaying could be one of the following:
You are not looking at the same control as you are setting the text in
Could you have instantiated a second copy of the form object and it is this form that you are setting the txtAttach text property in?
Could the control that you are expecting to be populated be a different one? Right click the text box that you want the text to appear in click properties and check the name.
Something else is clearing the textbox after you set it
Right click the txtAttach.Text and click Find All References, this will show you all the places that the Text property is referenced - written and read - in your project. This is a very useful way to locate other interaction with this control.
Fomatting is making the text box appear empty
Is the Font too small, or in the same colour as the background. Can you select the text in the text box?
The easiest way to test all of the above is to create a new text control on your form with a different name, change your code to populate it, check that it is indeed populated, then replace the old one.
As an aside, you could also reduce the code with a single line as follows:
public void fillAttachment(List<string> attachList)
{
txtAttach.Text = String.Join(";", attachList.ToArray());
}
Although this obviously skips out the console write line function.

Not sure why yours doesn't work but I would have done it like this...
public void fillAttachment(List<string> attachList)
{
string result = "";
//OR (if you want to append to existing textbox data)
//string result = txtAttach.Text;
for (int i = 0; i < attachList.Count; i++)
{
Console.WriteLine("List: " + attachList[i]);
result += attachList[i] + ";";
}
txtAttach.Text = result;
}
Does that work for you? If not then there is something else very wrong that is not obvious from your code