C＃里， 字符串问题（急！！！）

Question

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;namespace calc
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }        private void button1_Click(object sender, EventArgs e)
        {
            string strSrc = textBox1.Text.Trim();
            if (strSrc.Length > 0)
            {
                int idx = strSrc.IndexOf("=");
                if ((idx == strSrc.LastIndexOf("=")) && (idx > 0))
                {
                    strSrc = strSrc.Replace("-", "+-");                    string[] strTmp = strSrc.Split( '+' );
                    if (strTmp.Length > 0)
                    {
                        int nloop = 0;
                        int a = 0, b = 0, c = 0, value = 0;
                        
                        string[] arrValue = strTmp[strTmp.Length-1].Split( '=' );
                        strTmp[strTmp.Length - 1] = arrValue[0].Trim();
                        string strValue = arrValue[1].Trim();
                        value = int.Parse(strValue);                        if (nloop < strTmp.Length)
                        {
                            string strA = strTmp[nloop].Trim().Replace("x*x", "").Trim();
                            if (strA.Length < strTmp[nloop].Trim().Length)
                            {
                                strA = strA.Replace(" ", "");
                                if (strA.Length > 0)
                                {
                                    a = int.Parse(strA);
                                    nloop++;
                                }
                            }
                        }                        if (nloop < strTmp.Length)
                        {
                            string strB = strTmp[nloop].Trim().Replace("x", "").Trim();
                            if (strB.Length < strTmp[nloop].Trim().Length)
                            {
                                strB = strB.Replace(" ", "");
                                if (strB.Length > 0)
                                {
                                    b = int.Parse(strB);
                                    nloop++;
                                }
                            }
                        }                        if (nloop < strTmp.Length)
                        {
                            string strC = strTmp[nloop].Trim();
                            strC = strC.Replace(" ", "");
                            if (strC.Length > 0)
                            {
                                c = int.Parse(strC);
                            }
                        }                        c = c - value;                        // -b(+-)sqrt(b^2-4ac) / (2 * a)
                        value = b * b - 4 * a * c;
                        if( value < 0 )
                        {
                            //在实数范围内无解
                        }
                        else 
                        {
                            double x1, x2;                            if (a != 0)
                            {
                                double dblTmp = System.Math.Sqrt(value);
                                x1 = (-1 * b + dblTmp) / (2 * a);
                                x2 = (-1 * b - dblTmp) / (2 * a);
                            }
                            else
                            {
                                x1 = x2 = -1.0 * c / b;
                            }                            Console.WriteLine("x1 = " + x1.ToString() + " , x2 = " + x2.ToString());
                        }
                    }
                    else
                    {
                        //格式错误
                    }
                }
                else
                {
                    //格式错误
                }
            }
        }
    }
}注：按此格式输入方程
ax*x + bx + c = value
方程左边等于0的项可以省略不写，方程右边如果等于0则必须写0，如果a、b的值为 1，也必须写出来，请注意乘号( * )仅在x*x中出现
另外，代码没有对形如 0 = 8 等不合理的式子做判断举例
输入
2x*x - 4x + 16 = 23
输出
x1 = 3.12132034355964 , x2 = -1.12132034355964输入
8x+7=25
输出
x1 = 2.25 , x2 = 2.25输入
2x*x + 3 = 11
输出
x1 = 2 , x2 = -2