如何使用 Delete 键删除 Excel 列表对象列？

Question

When the active cell in an Excel listobject is a column header, I would like to programmatically (in C#) handle pressing the DEL key as the equivalent to deleting that column. Currently, if I press the DEL key, the header name will change into a default name automatically generated by Excel (eg List1, or Spalte1 in my case of a German version of Excel).

Trapping a keypress event for the DEL key is an option I would like to avoid, as I don't want to stress unnecessarily the application by permanently having to monitor for any kind of keypress events.

Therefore, I am wondering if there is any way to determine what the default naming of the column header will be after pressing the Delete key, so that I can implement a Change event handler which will compare the new header content with that default name, and thus interpret this as a column delete action (of course asking the user for confirmation!).

In the change event handler, the code could look like this (here, it is assumed that ActiveCell is the header column name of the column that is to be removed):

string headerName = ActiveCell.Value2;
int colIdx = ActiveCell.Column - myListObject.Range.Column +1;
Excel.ListColumn columnToDelete = myListObject.ListColumns[colIdx];
if (headerName == someDefaultName)
{
    columnToDelete.Delete();
}

Is there anyway how I can determine someDefaultName without having to compare with a list of default names for all possible languages supported by Excel??

Answer 1

Below is my idea. It is based on following worksheet:

with the ListObject "list1". It contains 5 columns. The main idea - is to add a new column on the startup, catch it's header, remove numbers from this text and put it into a variable to compare changes sent by ListObject_Change event. As soon as someone presses Del on the header row - it will be changed to default name and deleted. Nevertheless, it would not delete a new column with default name.

public partial class Sheet1
{
    // assign temp variables for header range and a column name
    // template
    public Excel.Range HeaderRange { get; set; }
    public string template;


    private void Sheet1_Startup(object sender, System.EventArgs e)
    {
        // subscribe to ListObject change event
        list1.Change += new Microsoft.Office.Tools.Excel.ListObjectChangeHandler(list1_Change);
        // get the template on start (switch of events for a while)
        this.Application.EnableEvents = false;
        GetDefaultColumnHeaderTemplate();
        this.Application.EnableEvents = true;
    }

    private void Sheet1_Shutdown(object sender, System.EventArgs e)
    {
    }


    //ListObject change event:
    void list1_Change(Microsoft.Office.Interop.Excel.Range targetRange, Microsoft.Office.Tools.Excel.ListRanges changedRanges)
    {
        // assign variables to simplify the code below
        Excel.Range Intersection = Globals.Sheet1.Application.Intersect((Excel.Range)targetRange, HeaderRange);
        HeaderRange = list1.HeaderRowRange;

        // if range is assigned - means that change was done in header row
        if (!(Intersection == null))
        {
            // make sure that changed range is only one cell
            if (Intersection.Rows.Count < 2 && Intersection.Columns.Count < 2)
            {
                // if this cell contains template - delete entire column 
                if ((targetRange.Value2).ToString().Contains(template))
                {
                    targetRange.EntireColumn.Delete();
                }
            }
        }
    }

    private void GetDefaultColumnHeaderTemplate()
    {
        // add a column with default name
        Excel.ListColumn tempColumn = list1.ListColumns.Add();

        // re-assign headers range
        HeaderRange = list1.HeaderRowRange;

        // catch the name of new column with default name
        // and remove a number  counter
        template = GetTextTemplate(HeaderRange.Cells[1, HeaderRange.Columns.Count].Value2.ToString());

        // delete temp column
        tempColumn.Delete();
    }

    private string GetTextTemplate(string tx)
    {
        string tmp = null;

        // go through each char of default column name and take only letters
        for (int i = 0; i < tx.Length; i++)
        {
            if (!double.TryParse(tx.Substring(i, 1), out _))
            {
                tmp += tx.Substring(i, 1);
            }
        }
        return tmp;
    }
        #region VSTO Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
    private void InternalStartup()
    {
        this.Startup += new System.EventHandler(this.Sheet1_Startup);
        this.Shutdown += new System.EventHandler(this.Sheet1_Shutdown);

    }

    #endregion

}