C#

endo funk wrote:

Yes; first off IEnumerable was Microsoft implementation of functional programming algebras for a List. It is essentially a monadic data type that encapsulates List; monadic data types are typically designed to conform to a fairly standard set of functional algebras i.e. providing a common API for computations.

endo funk wrote:

Extension methods... apparently so obvious that you missed it.

Quote:

Imagine you have bright young student sitting down with you, whom you've introduced to Linq, and generics ... and, they've had no problems mastering 'Select and 'Where, 'Aggregate, etc.

You have introduced them to the use of 'yield return' in a method to return an IEnumerable they can turn into an instance of a collection. They "get that," and get use of yield means they can skip direct assignment to a pre-defined, initialized collection, or, a collection instance reference passed in as an 'out parameter.

And you are trying to explain to them the "deferred iteration/evaluation" aspect of IEnumerable, and the way that enables some advanced practices (function chaining).

matBaseBindingSource.Filter = "USnumber = '" + cmbBaseM.SelectedItem + "'";

matBaseBindingSource.Filter = $"USnumber = '{cmbBaseM.SelectedItem}'";

private void ComboBox_SelectedIndexChanged(object sender, EventArgs e)
{
    string[] comboSelections =
    {
        CmbBaseM.SelectedIndex != -1
			? $"BaseM = '{CmbBaseM.GetItemText(CmbBaseM.SelectedItem)}'"
			: string.Empty,
        CmbUmat.SelectedIndex != -1
			? $"Umat = '{CmbUmat.GetItemText(CmbUmat.SelectedItem)}'"
			: string.Empty,
        CmbGmat.SelectedIndex != -1
			? $"Gmat = '{CmbGmat.GetItemText(CmbGmat.SelectedItem)}'"
			: string.Empty
    };
    string filter = string.Join(" AND ", comboSelections.Where(s => !string.IsNullOrEmpty(s)));
    MyBindingSource.Filter = filter;
}

CmbUmat

  using System;
using System.Drawing;
using System.Windows.Forms;
using Spire.Barcode;

namespace camera2
{
    public partial class Form2 : Form
    {
        Bitmap bitmap;
        //

<pre>
    public Form2()
    {
        InitializeComponent();
    }

    private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
    {
      //  using System.Drawing.Printing;
        e.Graphics.DrawImage(bitmap, 0, 0);
    }

    private void CaptureScreen()
    {
        Graphics myGraphics = this.CreateGraphics();
        Size s = this.Size;
        bitmap = new Bitmap(s.Width, s.Height, myGraphics);
        Graphics memoryGraphics = Graphics.FromImage(bitmap);
        memoryGraphics.CopyFromScreen(this.Location.X, this.Location.Y, 0, 0, s);
    }
    private void print_Click(object sender, EventArgs e)
    {
        PrintDialog pDialog = new PrintDialog();
        pDialog.AllowSomePages = true;
        if (pDialog.ShowDialog(this) == DialogResult.OK)
        // this.printDoc.Print();
        {
           // Front card panel 1 
            Panel panel = new Panel();
            panel1.Size = new System.Drawing.Size(600,600);
            this.Controls.Add(panel);
            Graphics grp = panel.CreateGraphics();
            Size formSize = this.ClientSize;
            bitmap = new Bitmap(formSize.Width, formSize.Height, grp);
            grp = Graphics.FromImage(bitmap);
            Point panelLocation = PointToScreen(panel.Location);
            grp.CopyFromScreen(panelLocation.X, panelLocation.Y, 0, 0, formSize);
            printPreviewDialog1.Document = printDocument1;
            printPreviewDialog1.PrintPreviewControl.Zoom = 1;
            printPreviewDialog1.ShowDialog();

            // back card panel 2

            Panel panel2 = new Panel();
            panel2.Size = new System.Drawing.Size(600, 600);
            this.Controls.Add(panel);
            Graphics grp1 = panel.CreateGraphics();
            Size formSize1 = this.ClientSize;
            bitmap = new Bitmap(formSize.Width, formSize.Height, grp);
            grp1 = Graphics.FromImage(bitmap);
            Point panelLocation1 = PointToScreen(panel2.Location);
            grp.CopyFromScreen(panelLocation1.X, panelLocation1.Y, 0, 0, formSize1);
            printPreviewDialog1.Document = printDocument1;
            printPreviewDialog1.PrintPreviewControl.Zoom = 1;
            printPreviewDialog1.ShowDialog();

        }
    }