product of two multiline textboxes and display it also to another multiline textbox

Question

I want to know how to perform calculations such as multiplication of two multiline textboxes and the product of it will also display in a multiline textbox. Please see the design below

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Answer 1

If you want to get the multiplication of two multiline textboxes and display the result in a multiline textbox, you can use the following code：

private void textBox2_LostFocus(object sender, EventArgs e)
    {
        float a, b;
        for (int i = 0; i < textBox1.Lines.Length ; i++)
        {

            float.TryParse(textBox1.Lines[i], out a);
            float.TryParse(textBox2.Lines[i], out b);
            textBox3.AppendText((a * b).ToString()+ Environment.NewLine);
        }
    }

And you have to add an EventHandler in Form1.Designer.cs file:

        // 
        // textBox2
        // 
        this.textBox2.Location = new System.Drawing.Point(312, 110);
        this.textBox2.Multiline = true;
        this.textBox2.Name = "textBox2";
        this.textBox2.Size = new System.Drawing.Size(100, 167);
        this.textBox2.TabIndex = 4;
        this.textBox2.LostFocus += new System.EventHandler(this.textBox2_LostFocus);