You can very easily solve
a Quadratic Equation with this small program. Just enter the values in
the 3 text boxes and you will find the resulting roots(solutions) of the
Quadratic equation on the right. Watch the final output and see the
source code further below:
 |
| Solve Quadratic Equation in C# WinForms Application |
The
C# Code below is simple, structured & complete. Note the code for
the text box change event is similar for all the 3 text boxes.
namespace Solve_Quadratic_Equation
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
double a, b, c;
Code to be used if the Determinant of Quadratic Equation is positive; This code returns the value to be used when the square root of the determinant is a real number.
public double DeterminantQuad(double b, double a, double c)
{
return ((b * b) - (4 * a * c));
}
Code to be used if Determinant of Quadratic Equation is negative; The code below returns the negative value of the regular determinant. Since the regular determinant is negative, we get a positive value in the end(negative of negative is positive). We then add the letter "i" in the answer to show that the square root is taken of a negative number. Therefore pointing out the unreal root in red color.
public string NegativeDeterminant(double b, double a, double c)
{
return (((4 * a * c) - (b * b)).ToString());
}
Calculate the First Root of the equation:
 |
| Quadratic Equation 1st Root C# Code |
public string FirstRealRootQuad(double a, double b, double c)
{
if (DeterminantQuad(b, a, c) >= 0)
{
return ((((-b) + (Math.Sqrt(DeterminantQuad(b, a, c)))) / (2 * a)).ToString());
}
else
{ return ((-b / (2 * a)).ToString() + "+ i" + (Convert.ToDouble(NegativeDeterminant(b,
a, c)) / (2 * a)).ToString()); }
}
Calculate the Second Root of the equation:
 |
| Quadratic Equation 2nd Root C# Code |
public string SecondRealRootQuad(double a, double b, double c)
{
if (DeterminantQuad(b, a, c) >= 0)
{
return ((((-b) - (Math.Sqrt(DeterminantQuad(b, a, c)))) / (2 * a)).ToString());
}
else
{ return ((-b / (2 * a)).ToString() + "- i" + (Convert.ToDouble(NegativeDeterminant(b,
a, c)) / (2 * a)).ToString()); }
}
TextBox Text Change Event Code; This code is similar for all the 3 Text Boxes
private void QuadA_TextChanged(object sender, EventArgs e)
{
try
{
a = Convert.ToDouble(QuadA.Text);
b = Convert.ToDouble(QuadB.Text);
c = Convert.ToDouble(QuadC.Text);
QuadRootA.Text =
FirstRealRootQuad(a, b, c);
QuadRootB.Text =
SecondRealRootQuad(a, b, c);
}
catch { }
if (QuadRootA.Text.Contains("i"))
{
QuadRootA.ForeColor = Color.Red;
}
if (QuadRootB.Text.Contains("i"))
{
QuadRootB.ForeColor = Color.Red;
}
}
}