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How can I detect if there are duplicates in a C# array and can I replace them with another suitable value in the same place in the array?

I'm kind of new to C# and I'm trying to make a sudoku game. I'm using a for loop to loop through the column arrays and add a random number to the spots but I'm using Random and Next() so it allows the numbers to repeat. But because I can't have more than one of a number in each column (array) for it to function, how can I replace the repeated number with another number that isn't repeated? I don't know how to do this.
Also the columns are stored in other arrays that I've called rows just so that I can say Row1[0][2] to access position 3 in column 1 for example.
Here's the method & for loop I'm using to replace add the numbers to the arrays:
void populateColumns(int[][] arr) // goes through column arrays and replaces the numbers with random ones from Num()
{
int i;
int j = 0;
for (int l = 0; l <= 8; l++)
{
for (i = 0; i <= 8; i++)
{
arr[j][i] = Num();
int currentPos = arr[j][i];
Console.Write(currentPos);
}
j = l;
}
}

smoothing stacked line graph

I have a c# Windows forms application that generates a stacked line graph using the standard MS Chart control, as in the below example.
Is there a way of "smoothing" the lines by formatting the series or some other property?
Looking at MSDN and Google I can't seem to find a way to do this, in Excel there a series.Smooth property...
I have I missed it or is it not possible?

If you liked the smooth look of the SplineAreas you can calculate the necessary values to get just that look:
A few notes:
I have reversed the order of the series; many ways to get the colors right.. (Instead one probably should accumulate in reverse)
The stacked DataPoints need to be aligned, as usual and any empty DataPoints should have their Y-Values to be 0.
Of course in the new series you can't access the actual data values any longer as you now have the accumulated values instead; at least not without reversing the calulation. So if need them keep them around somewhere. The new DataPoints' Tag property is one option..
You can control the ' smoothness' of each Series by setting its LineTension custom attribute:
chart2.Series[0].SetCustomProperty("LineTension", "0.15");
Here is the full example code that creates the above screenshots calculating a 'stacked' SplineArea chart2 from the data in a StackedArea chart1:
// preparation
for (int i = 0; i < 4; i++)
{
Series s = chart1.Series.Add("S" + i);
s.ChartType = SeriesChartType.StackedArea;
Series s2 = chart2.Series.Add("S" + i);
s2.ChartType = SeriesChartType.SplineArea;
}
for (int i = 0; i < 30; i++) // some test data
{
chart1.Series[0].Points.AddXY(i, Math.Abs(Math.Sin(i / 8f)));
chart1.Series[1].Points.AddXY(i, Math.Abs(Math.Sin(i / 4f)));
chart1.Series[2].Points.AddXY(i, Math.Abs(Math.Sin(i / 1f)));
chart1.Series[3].Points.AddXY(i, Math.Abs(Math.Sin(i / 0.5f)));
}
// the actual calculations:
int sCount = chart1.Series.Count;
for (int i = 0; i < chart1.Series[0].Points.Count ; i++)
{
double v = chart1.Series[0].Points[i].YValues[0];
chart2.Series[sCount - 1].Points.AddXY(i, v);
for (int j = 1; j < sCount; j++)
{
v += chart1.Series[j].Points[i].YValues[0];
chart2.Series[sCount - j - 1].Points.AddXY(i, v);
}
}
// optionally control the tension:
chart2.Series[0].SetCustomProperty("LineTension", "0.15");

listboxes passing values from each other

I'm trying to multiply the values of 2 listboxes together and make their product appear at another list box I'm getting the results I need but the problem is when I rerun the loop using a command button the listbox removes the next instance of the first value calculated by ppc[i] * qty[i] but when I try to remove the the listBox4.Items.Remove(ppc[i] * qty[i]) it reprints the whole array again from first element to last element
string myString = textBox1.Text.ToString();
int index = listBox6.FindString(myString, -1);
int[] qty = new int[99];
int[] ppc = new int[99];
int[] gt1 = new int[99];
listBox3.Items.Add(listBox5.Items[index]);
listBox1.Items.Add(textBox2.Text.ToString());
if (index != -1)
{
listBox6.SetSelected(index, true);
listBox2.Items.Add(textBox1.Text); //name
}
listBox3.Items.Add(listBox5.Items[index]);
listBox3.Items.Remove(listBox5.Items[index]);
for (int i = 0; i != listBox2.Items.Count ; i++)
{
ppc[i] = Convert.ToInt32(listBox3.Items[i]);
qty[i] = Convert.ToInt32(listBox1.Items[i]);
listBox4.Items.Remove(ppc[i] * qty[i]);
listBox4.Items.Add((ppc[i] * qty[i]));
}

My understanding is that this loop works once, and then when it is re-run it is out of order. Are you making sure to clear listbox4 each time this loop is executed? Also since listBox2 isn't used, it is probably better not to use it for your loop bounds.
if(listBox1.Items.Count == listBox3.Items.Count)
{
int rowCount = listBox1.Items.Count;
listBox4.Items.Clear();
for (int i=0; i < rowCount; i++)
{
ppc[i] = Convert.ToInt32(listBox3.Items[i]);
qty[i] = Convert.ToInt32(listBox1.Items[i]);
listBox4.Items.Insert(i , (ppc[i] * qty[i]));
}
}

Modifying Variable Names in C#

I'm not sure if the title is correct because I wasn't sure how to explain it. I've encountered many scenarios where being able to dynamically modify part of a variable name such a suffixing integer could save me a great deal of time and keep my code much cleaner but I'm not sure how to do it. Here's an example of my most recent encounter.
I have 9 PictureBox's in a 3 x 3 grid. Each PictureBox has a name of cell followed by it's number so cell1, cell2, cell3 etc. I want to get the background colour of each of these cells and assign them to a variable whilst converting them to strings... something like this:
for (int i = 1; i < 10; i++)
{
string ci = celli.BackColor.ToString();
}
Is there a way I can have the i variable insert only it's numeric value to the placeholder rather than appending an i to the variable name? Can I wrap it in some sort of bracket? I've tried Googleing this but I'm finding it difficult to search for using just keywords.
Thanks in advance.

You are probably using a visual form editor, the best way to do this whould probably be to generate the grid by code (and not visually).
Another solution is to make it a matrix:
PictureBox[,] cell = new PictureBox[,] {
{ cell1, cell2, cell3 },
{ cell4, cell5, cell6 },
{ cell7, cell8, cell9 }
};
string[,] c = new string[3, 3];
for(int y=0; y<3; y++)
for(int x=0; x<3; x++)
c[x, y] = cell[x, y].BackColor.ToString();
Good luck with your code.

You would like to generate a list or collection of all your pictureboxes so that you can access them by specifying their index. One way is to generate the PictureBoxes on runtime:
Like this:
List<PictureBox> myPics = new List<PictureBox>();
int picWidth = 100;
int picHeight = 100;
for (x = 0; x <= this.Width; x += picWidth) {
for (y = 0; y <= this.Height; y += picHeight) {
PictureBox pic = new PictureBox();
pic.Image = pic.Image;
// Your image
pic.Location = new Point(x, y);
this.Controls.Add(pic);
myPics.Add(pic);
}
}
// Do something with myPics...
The other method is that when you do have all the pictureboxes on your form already, you can iterate through all the controls, check which ones are pictureboxes and then check their Name property to identify their index. Then do something with them accordingly.
foreach (void ctrl_loopVariable in this.Controls) {
ctrl = ctrl_loopVariable;
if (ctrl.GetType() == typeof(PictureBox)) {
if (ctrl.Name == "your picture box name to test") {
// Do something here with ctrl
}
}
}
(The above code is converted from VB to C#, excuse conversion issues)

Your intend here is to dynamically reference those controls.
In order to achieve this, there is two options:
You create those controls dynamically
You create dynamic references for the controls created by your form-designer
The first point is explained ny Shreyas Kapur's answer.
The second could be cone like this,
readonly Dictionary<Point,PictureBox> _dynamicMappedBoxes =
new Dictionary<Point,PictureBox>();
// Call this once in the beginning ofr your program
void createDynamicMapping()
{
foreach(PictureBox box in Controls.OfType<PictureBox>())
{
Point coords = getCoordinatesFromName(box);
_dynamicMappedBoxes.Add(coords, box);
}
}
Point getCoordinatesFromName(PictrueBox box)
{
int x = int.Parse(box.Name.SubString(IdontKnow);
int y = int.Parse(box.Name.SubString(IdontKnow);
retrun new Point(x,y);
}
//usage
string colorName = dynamicMappedBoxes[new Point(x,y)].BackColor.ToString();

get value from datagrid cell in C#

How do I get the info from a certain cell in a data grid? I want an event to happen when a person clicks the button in the 7th column, but the event depends on the value in the first column. here's what i have, but nothing is happening.
if (InventoryDataGridView.CurrentCell.ColumnIndex == 7)
{
if(InventoryDataGridView[0,0].Equals("Books"))
{
Books open = new Books();
open.Show();
}
}
Nothing happens though

InventoryDataGridView[0,0]
only refers to the DataGridViewCell. That class has a Value property which contains the value of the cell.
so that line should look like this:
if(InventoryDataGridView[0,0].Value.Equals("Books"))
{
//
}

If you using WPF then you must try this:
for (int j = 0; j < dataGrid1.Columns.Count; j++)
{
for (int i = 0; i < dataGrid1.Items.Count - 1; i++)
{
string s=(dataGrid1.Items[i] as DataRowView).Row.ItemArray[j].ToString();
}
}
i,j are the co-ordinates. So you can play around it.
reference: http://subrat308.blogspot.in/2012/02/wpf-get-cell-value-from-datagrid-cellij.html