99/10/7 三成三矩陣

String output;
            int a=0, b=0, c=0;
            a = int.Parse(textBox1.Text);
            b = int.Parse(textBox2.Text);
            c = a * b;
            output = Convert.ToString(c);
            textBox3.Text = output;
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String output;
            int[,] a = new int[4, 4];
            int[,] b = new int[4, 4];
            int[,] c = new int[4, 4];
            a[1, 1] = int.Parse(textBox1.Text);
            a[1, 2] = int.Parse(textBox2.Text);
            a[1, 3] = int.Parse(textBox3.Text);
            a[2, 1] = int.Parse(textBox4.Text);
            a[2, 2] = int.Parse(textBox5.Text);
            a[2, 3] = int.Parse(textBox6.Text);
            a[3, 1] = int.Parse(textBox7.Text);
            a[3, 2] = int.Parse(textBox8.Text);
            a[3, 3] = int.Parse(textBox9.Text);
            b[1, 1] = int.Parse(textBox10.Text);
            b[1, 2] = int.Parse(textBox11.Text);
            b[1, 3] = int.Parse(textBox12.Text);
            b[2, 1] = int.Parse(textBox13.Text);
            b[2, 2] = int.Parse(textBox14.Text);
            b[2, 3] = int.Parse(textBox15.Text);
            b[3, 1] = int.Parse(textBox16.Text);
            b[3, 2] = int.Parse(textBox17.Text);
            b[3, 3] = int.Parse(textBox18.Text);
           

            c[1, 1] = a[1, 1] * b[1, 1] + a[1, 2] * b[2, 1] + a[1, 3] * b[3, 1];
            c[1, 2] = a[1, 1] * b[1, 2] + a[1, 2] * b[2, 2] + a[1, 3] * b[3, 2];
            c[1, 3] = a[1, 1] * b[1, 3] + a[1, 2] * b[2, 3] + a[1, 3] * b[3, 3];
           
            c[2, 1] = a[2, 1] * b[1, 1] + a[2, 2] * b[2, 1] + a[2, 3] * b[3, 1];
            c[2, 2] = a[2, 1] * b[1, 2] + a[2, 2] * b[2, 2] + a[2, 3] * b[3, 2];
            c[2, 3] = a[2, 1] * b[1, 3] + a[2, 2] * b[2, 3] + a[2, 3] * b[3, 3];
            c[3, 1] = a[3, 1] * b[1, 1] + a[3, 2] * b[2, 1] + a[3, 3] * b[3, 1];
            c[3, 2] = a[3, 1] * b[1, 2] + a[3, 2] * b[2, 2] + a[3, 3] * b[3, 2];
            c[3, 3] = a[3, 1] * b[1, 3] + a[3, 2] * b[2, 3] + a[3, 3] * b[3, 3];
            output = Convert.ToString(c[1, 1]);
            textBox19.Text = output;
            output = Convert.ToString(c[1, 2]);
            textBox20.Text = output;
            output = Convert.ToString(c[1, 3]);
            textBox21.Text = output;
            output = Convert.ToString(c[2, 1]);
            textBox22.Text = output;
            output = Convert.ToString(c[2, 2]);
            textBox23.Text = output;
            output = Convert.ToString(c[2, 3]);
            textBox24.Text = output;
           
            output = Convert.ToString(c[3, 1]);
            textBox25.Text = output;
            output = Convert.ToString(c[3, 2]);
            textBox26.Text = output;
            output = Convert.ToString(c[3, 3]);
            textBox27.Text = output;