C# what causes a variable to show as "xxxx is not available within the current context

Question

I am having some trouble with code I'm trying to use to export some data to excel through a button click. I cant seem to figure out what I am doing wrong.

In my code, I have an ExcelExport class which contains the following code

 class ExcelExport
{
    DirectoryInfo outputDir = new DirectoryInfo(@"c:\temp\SampleApp");
    /// <summary>
    /// ExcelExport simply creates a new workbook from scratch.
    /// The workbook contains one worksheet with a simple invertory list
    /// </summary>
    public static string RunSample1(DirectoryInfo outputDir)
    {

        if (!outputDir.Exists) throw new Exception("outputDir does not exist!");
        FileInfo newFile = new FileInfo(outputDir.FullName + @"\sample1.xlsx");
        if (newFile.Exists)
        {
            newFile.Delete();  // ensures we create a new workbook
            newFile = new FileInfo(outputDir.FullName + @"\sample1.xlsx");
        }
        using (ExcelPackage package = new ExcelPackage(newFile))
        {
            // add a new worksheet to the empty workbook
            ExcelWorksheet worksheet = package.Workbook.Worksheets.Add("Inventory");
            //Add the headers
            worksheet.Cells[1, 1].Value = "ID";
            worksheet.Cells[1, 2].Value = "Product";
            worksheet.Cells[1, 3].Value = "Quantity";
            worksheet.Cells[1, 4].Value = "Price";
            worksheet.Cells[1, 5].Value = "Value";

            //Add some items...
            worksheet.Cells["A2"].Value = 12001;
            worksheet.Cells["B2"].Value = "Nails";
            worksheet.Cells["C2"].Value = 37;
            worksheet.Cells["D2"].Value = 3.99;

            worksheet.Cells["A3"].Value = 12002;
            worksheet.Cells["B3"].Value = "Hammer";
            worksheet.Cells["C3"].Value = 5;
            worksheet.Cells["D3"].Value = 12.10;

            worksheet.Cells["A4"].Value = 12003;
            worksheet.Cells["B4"].Value = "Saw";
            worksheet.Cells["C4"].Value = 12;
            worksheet.Cells["D4"].Value = 15.37;

            //Add a formula for the value-column
            worksheet.Cells["E2:E4"].Formula = "C2*D2";

            //Ok now format the values;
            using (var range = worksheet.Cells[1, 1, 1, 5])
            {
                range.Style.Font.Bold = true;
                range.Style.Fill.PatternType = ExcelFillStyle.Solid;
                range.Style.Fill.BackgroundColor.SetColor(Color.DarkBlue);
                range.Style.Font.Color.SetColor(Color.White);
            }

            worksheet.Cells["A5:E5"].Style.Border.Top.Style = ExcelBorderStyle.Thin;
            worksheet.Cells["A5:E5"].Style.Font.Bold = true;

            worksheet.Cells[5, 3, 5, 5].Formula = string.Format("SUBTOTAL(9,{0})", new ExcelAddress(2, 3, 4, 3).Address);
            worksheet.Cells["C2:C5"].Style.Numberformat.Format = "#,##0";
            worksheet.Cells["D2:E5"].Style.Numberformat.Format = "#,##0.00";

            //Create an autofilter for the range
            worksheet.Cells["A1:E4"].AutoFilter = true;

            worksheet.Cells["A2:A4"].Style.Numberformat.Format = "@";   //Format as text

            //There is actually no need to calculate, Excel will do it for you, but in some cases it might be useful. 
            //For example if you link to this workbook from another workbook or you will open the workbook in a program that hasn't a calculation engine or 
            //you want to use the result of a formula in your program.
            worksheet.Calculate();

            worksheet.Cells.AutoFitColumns(0);  //Autofit columns for all cells

            // lets set the header text 
            worksheet.HeaderFooter.OddHeader.CenteredText = "&24&U&\"Arial,Regular Bold\" Inventory";
            // add the page number to the footer plus the total number of pages
            worksheet.HeaderFooter.OddFooter.RightAlignedText =
                string.Format("Page {0} of {1}", ExcelHeaderFooter.PageNumber, ExcelHeaderFooter.NumberOfPages);
            // add the sheet name to the footer
            worksheet.HeaderFooter.OddFooter.CenteredText = ExcelHeaderFooter.SheetName;
            // add the file path to the footer
            worksheet.HeaderFooter.OddFooter.LeftAlignedText = ExcelHeaderFooter.FilePath + ExcelHeaderFooter.FileName;

            worksheet.PrinterSettings.RepeatRows = worksheet.Cells["1:2"];
            worksheet.PrinterSettings.RepeatColumns = worksheet.Cells["A:G"];

            // Change the sheet view to show it in page layout mode
            worksheet.View.PageLayoutView = true;

            // set some document properties
            package.Workbook.Properties.Title = "Invertory";
            package.Workbook.Properties.Author = "Jan Källman";
            package.Workbook.Properties.Comments = "This sample demonstrates how to create an Excel 2007 workbook using EPPlus";

            // set some extended property values
            package.Workbook.Properties.Company = "AdventureWorks Inc.";

            // set some custom property values
            package.Workbook.Properties.SetCustomPropertyValue("Checked by", "Jan Källman");
            package.Workbook.Properties.SetCustomPropertyValue("AssemblyName", "EPPlus");
            // save our new workbook and we are done!
            package.Save();

        }

        return newFile.FullName;
    }
}

I am trying to run that code from a button click by doing this

 ExcelExport.RunSample1(DirectoryInfo.outputDir);

In that line outputDir is generating the "name is not available in the current context" error. What exactly causes this?

Answer 1

As originally mentionned in my comment:

1. Recompile in Debug mode instead of release
2. Make sure to rebuild all when you do (so that it will delete temporary files that release mode might have created

Generally release mode don't keep variables information, and because of that you can't "connect" to a variable to see it while debugging with Visual studio because a part is missing.

Answer 2

DirectoryInfo outputDir = new DirectoryInfo(@"c:\temp\SampleApp");

This creates a private instance variable for the ExcelExport type.

public static string RunSample1(DirectoryInfo outputDir)

This creates a static method for the same type. Static methods do not have access to instance variables because there is no instance.

Instead, make the variable static:

public static DirectoryInfo outputDir = new DirectoryInfo(@"c:\temp\SampleApp");