1、从网上找了个中缀算法(也不知道什么前缀后缀，抱歉),可以对字符串表达式进行运算
2、有些时候还是会用到ASCII码表的
char c = expression[k];//expression为一字符串
int intAsciiCode = (int)c;
3、里面用到了解决多种字符串日期显示格式，转换为日期类型的办法
DateTime time = DateTime.Now;
DateTimeFormatInfo dtfi = new CultureInfo("zh-CN", true).DateTimeFormat;
DateTime.TryParseExact(strTime, new string[] { "yyyyMMdd", "yyyy.M.d", "d-M-yyyy", "d-M月-yyyy", "yyyy-M-d", "yyyy_M_d" }, dtfi, DateTimeStyles.None, out time);//strTime为字符串类型日期
1 public class DataTableCompute 2 { 3 /// <summary> 4 /// 对DataTabella行上的列根据运算式计算 5 /// </summary> 6 /// <param name="dicDecimal">数值类型表达式键值对</param> 7 /// <param name="dicTime">时间类型表达式键值对</param> 8 /// <param name="row">DataTable表上的行</param> 9 public static void ComputeColumns(Dictionary<string, string> dicDecimal, Dictionary<string, string> dicTime, DataRow row) 10 { 11 if (dicDecimal != null && dicDecimal.Count > 0) 12 { 13 foreach (KeyValuePair<string, string> kvp in dicDecimal) 14 { 15 GetExpressionByType(row, kvp, "decimal"); 16 } 17 } 18 if (dicTime != null && dicTime.Count > 0) 19 { 20 foreach (KeyValuePair<string, string> kvp in dicTime) 21 { 22 GetExpressionByType(row, kvp, "time"); 23 } 24 } 25 26 } 27 28 private static void GetExpressionByType(DataRow row, KeyValuePair<string, string> kvp, string type) 29 { 30 string result = kvp.Key; 31 string expression = kvp.Value; 32 string[] cols = expression.Split(new char[] { '(', ')', '+', '-', '*', '/', '\' },StringSplitOptions.RemoveEmptyEntries); 33 for (int m = 0; m < cols.Length; m++) 34 { 35 if (type == "time") 36 { 37 DateTime time = DateTime.Now; 38 if (cols[m].ToLower() != "now") 39 { 40 DateTimeFormatInfo dtfi = new CultureInfo("zh-CN", true).DateTimeFormat; 41 if (!DateTime.TryParseExact(row[cols[m]].ToString(), new string[] { "yyyyMMdd", "yyyy.M.d", "d-M-yyyy", "d-M月-yyyy", "yyyy-M-d", "yyyy_M_d" }, dtfi, DateTimeStyles.None, out time)) 42 { 43 time = DateTime.Now; 44 } 45 } 46 cols[m] = (time.Year * 12 + time.Month).ToString(); 47 } 48 else 49 { 50 double d = 0; 51 if (double.TryParse(row[cols[m]].ToString(), out d)) 52 { 53 d = Math.Round(d, 3); 54 } 55 cols[m] = d.ToString(); 56 } 57 } 58 StringBuilder newExpression = new StringBuilder(); 59 int n = 0; 60 for (int k = 0; k < expression.Length; k++) 61 { 62 char c = expression[k]; 63 int intAsciiCode = (int)c; 64 if (intAsciiCode >= 40 && intAsciiCode <= 47) 65 { 66 newExpression.Append(c.ToString() + " "); 67 continue; 68 } 69 if (c == 'F' || c == 'n') 70 { 71 newExpression.Append(cols[n] + " "); 72 n++; 73 } 74 } 75 string str = newExpression.ToString(); 76 row[result] = CalculateResult(str); 77 } 78 private static double CalculateResult(string expre) 79 { 80 List<string> temp = getColuExpression(expre); 81 try 82 { 83 while (temp.Count > 1) 84 { 85 for (int i = 0; i < temp.Count; i++) 86 { 87 double resultTemp = 0; 88 if (temp[i] == "+") 89 resultTemp = Convert.ToDouble(temp[i - 2]) + Convert.ToDouble(temp[i - 1]); 90 else if (temp[i] == "-") 91 resultTemp = Convert.ToDouble(temp[i - 2]) - Convert.ToDouble(temp[i - 1]); 92 else if (temp[i] == "*") 93 resultTemp = Convert.ToDouble(temp[i - 2]) * Convert.ToDouble(temp[i - 1]); 94 else if (temp[i] == "/") 95 resultTemp = Convert.ToDouble(temp[i - 2]) / Convert.ToDouble(temp[i - 1]); 96 else 97 continue; 98 temp[i - 2] = resultTemp.ToString(); 99 temp.RemoveAt(i); 100 temp.RemoveAt(i - 1); 101 break; 102 } 103 } 104 } 105 catch (Exception ex)//计算表达式的值错误，导致无法运算 106 { 107 temp.Clear(); 108 temp.Add("0"); 109 } 110 return Convert.ToDouble(temp[0]); 111 } 112 private static List<string> getColuExpression(string exp) 113 { 114 System.Text.ASCIIEncoding asc = new System.Text.ASCIIEncoding(); 115 Stack st = new Stack(); 116 string[] temp = exp.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries); 117 List<string> value = new List<string>(); 118 119 for (int i = 0; i < temp.Length; i++) 120 { 121 int num = (int)asc.GetBytes(temp[i])[0]; 122 if (num < 48 && num > 39) 123 { 124 if (st.Count > 0) 125 { 126 string operatorStr = st.Peek().ToString(); 127 if (temp[i] == "*" || temp[i] == "/") 128 { 129 if (temp[i + 1] == "(") 130 { 131 st.Push(temp[i]); 132 133 continue; 134 } 135 else 136 { 137 if (operatorStr == "(") 138 { 139 st.Push(temp[i]); 140 continue; 141 } 142 else if (operatorStr == "*" || operatorStr == "/") 143 { 144 value.Add(st.Pop().ToString()); 145 st.Push(temp[i]); 146 continue; 147 } 148 else 149 { 150 st.Push(temp[i]); 151 continue; 152 } 153 } 154 } 155 else if (temp[i] == "+" || temp[i] == "-") 156 { 157 if (operatorStr == "(") 158 { 159 st.Push(temp[i]); 160 continue; 161 } 162 else 163 { 164 value.Add(st.Pop().ToString()); 165 if (st.Count > 0 && st.Peek().ToString() != "(") 166 { 167 value.Add(st.Pop().ToString()); 168 } 169 st.Push(temp[i]); 170 continue; 171 } 172 } 173 else if (temp[i] == "(") 174 { 175 st.Push(temp[i]); 176 continue; 177 } 178 else 179 { 180 if (i + 1 == temp.Length) 181 { 182 value.Add(st.Pop().ToString()); 183 st.Pop(); 184 while (st.Count > 0) 185 value.Add(st.Pop().ToString()); 186 break; 187 } 188 else 189 { 190 value.Add(st.Pop().ToString()); 191 st.Pop(); 192 continue; 193 } 194 } 195 } 196 else 197 { 198 st.Push(temp[i]); 199 continue; 200 } 201 } 202 else if (i + 1 == temp.Length) 203 { 204 value.Add(temp[i]); 205 value.Add(st.Pop().ToString()); 206 while (st.Count > 0) 207 value.Add(st.Pop().ToString()); 208 break; 209 } 210 else 211 { 212 value.Add(temp[i]); 213 continue; 214 } 215 } 216 return value; 217 } 218 }