C# to only run a block of code once

richard smith

You guys may be able to tell me a better way to do this, but what I am wanting to do is I have a statement in my C# that creates a new instance of excel then codes...for example:
_Application docExcel = new Microsoft.Office.Interop.Excel.Application();
docExcel.Visible = true;
docExcel.DisplayAlerts = false;
_Workbook workbooksExcel = docExcel.ActiveWorkbook;
workbooksExcel = (_Workbook)(docExcel.Workbooks.Add(XlWBATemplate.xlWBATWorksheet));
Worksheet worksheet = (Worksheet)docExcel.Worksheets["Sheet1"];

//more code down here to export datagrid to Excel

So with that being said, each time my function is called, I do not want it to run the above code, I only want it to run the above code if EXCEL IS NOT OPEN, OR this is the 1st time function is run. How can I do this in C#?

9 Replies

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Vulpes13y ago
Accepted answer
You'll need to make docExcel, workbooksExcel and worksheet into fields of the class rather than local variables. Something like this:

private _Application docExcel;
private _Workbook workbooksExcel;
private Worksheet worksheet;

private void ExcelMethod()
{
if (docExcel == null)
{
docExcel = new Microsoft.Office.Interop.Excel.Application();
docExcel.Visible = true;
docExcel.DisplayAlerts = false;
workbooksExcel = (_Workbook)(docExcel.Workbooks.Add(XlWBATemplate.xlWBATWorksheet));
worksheet = (Worksheet)docExcel.Worksheets["Sheet1"];
}

//more code down here to export datagrid to Excel
}
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richard smith13y ago
UGH! That is my error 99% of the time, i will have to commit that to memory! Thank you I am now up and running as desired.
0
Vulpes13y ago
If the error is on this line:

Worksheet sheetExcel = (Worksheet)(workbooksExcel.ActiveSheet;

then it must be because workBooksExcel hasn't been initialized at this point and so still has it's default value of null.

It might be best to disable buttons which assume that initialization has taken place until it has in fact been done.
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richard smith13y ago
I'm almost there...one more prob I hit...
namespace Test
{
class Testing
{
private static _Application docExcel;
private static _Workbook workbooksExcel;
private static Worksheets worksheet;

public static void btn1_Click()
{
//Trouble line of code...
Worksheet sheetExcel = (Worksheet)(workbooksExcel.ActiveSheet;
((Range)sheetExcel.Cells["1", "A"]).Value2 = "Name";
}

And I get a debug error of NullReferenceException was unhandled.
0
brunda k13y ago
http://stackoverflow.com/questions/12457240/how-can-i-open-the-current-instance-of-excel-from-my-application
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Vulpes13y ago
It sounds like you now have two external entities called 'worksheet' which are in scope and are causing a conflict i.e. the compiler doesn't know which one to choose.

Two possible ways to resolve it:

1. Change the name of the static field slightly to'workSheet. You'd then need to use this name throughout the method; or

2. When using 'worksheet' in the method always qualify it with the name of the enclosing class. So if, for example, the enclosing class is called Form1, then use Form1.worksheet within the method to distinguish it from the other 'worksheet'.
0

richard smith13y ago

You my friend REALLY know your C#....I am getting one more compile error.
//Decleration

private static Worksheet worksheet;

//Calling from within my method
worksheet.get_Range("A1", "W1").Font.Bold = true;



produces the error of 'worksheet' conflicts with the declaration 'namespace1.Testclass.worksheet'

Vulpes13y ago
Is your method static?

If it is, then make your fields static as well:

private static _Application docExcel;
private static _Workbook workbooksExcel;
private static Worksheet worksheet;
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richard smith13y ago
Moving docExcel I get a debug error of An object reference is required for the non-static field, method or property.
0