新增字符串扩展方法SubstringEx和Split方法。

Falcon.SugarApi.Test/StringExtendTest.cs

@@ -1,4 +1,7 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MySqlX.XDevAPI.Common;
+using System;
+using System.Linq;
 
 namespace Falcon.SugarApi.Test
 {
@@ -56,5 +59,59 @@ namespace Falcon.SugarApi.Test
             r = str.ToDefault("abc");
             Assert.AreEqual("123",r);
         }
+
+        /// <summary>
+        /// 检索子字符串测试
+        /// </summary>
+        [TestMethod]
+        public void TestSubstringEx() {
+            var str = "abcd33";
+            string r;
+            r = str.SubstringEx(str.Length + 1,1);
+            Assert.IsTrue(r == "");
+            r = str.SubstringEx(0,0);
+            Assert.IsTrue(r == "");
+            r = str.SubstringEx(3,-1);
+            Assert.IsTrue(r == "c");
+            r = str.SubstringEx(3,10);
+            Assert.IsTrue(r == "d33");
+            r = str.SubstringEx(-1,2);
+            Assert.IsTrue(r == "a");
+            r = str.SubstringEx(1,2);
+            Assert.IsTrue(r == "bc");
+
+        }
+
+        /// <summary>
+        /// 按一定长度分割字符串测试
+        /// </summary>
+        [TestMethod]
+        public void TestSplitByLength() {
+            string str;
+            string[] result;
+
+            str = "";
+            Assert.ThrowsException<ArgumentNullException>(() => { result = str.Split(5).ToArray(); });
+            str = "abc";
+            Assert.ThrowsException<Exception>(() => { result = str.Split(0).ToArray(); });
+            result = str.Split(1).ToArray();
+            Assert.IsTrue(result.Length == 3);
+            Assert.IsTrue(result[0] == "a");
+            Assert.IsTrue(result[1] == "b");
+            Assert.IsTrue(result[2] == "c");
+
+            result = str.Split(2).ToArray();
+            Assert.IsTrue(result.Length == 2);
+            Assert.IsTrue(result[0] == "ab");
+            Assert.IsTrue(result[1] == "c");
+
+            result = str.Split(3).ToArray();
+            Assert.IsTrue(result.Length == 1);
+            Assert.IsTrue(result[0] == "abc");
+
+            result = str.Split(4).ToArray();
+            Assert.IsTrue(result.Length == 1);
+            Assert.IsTrue(result[0] == "abc");
+        }
     }
 }

Falcon.SugarApi/StringExtend.cs

@@ -1,6 +1,9 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
+using System.Linq;
+using System.Reflection.Metadata;
 
 namespace Falcon.SugarApi
 {
@@ -66,8 +69,7 @@ namespace Falcon.SugarApi
             try {
                 dt = str.ToDateTime(dateTimeFormat,culture);
                 return true;
-            }
-            catch (Exception) {
+            } catch(Exception) {
                 dt = default;
                 return false;
             }
@@ -89,5 +91,55 @@ namespace Falcon.SugarApi
             }
             return str.TryToDateTime(dateFormat,out var _);
         }
+
+        /// <summary>
+        /// 获取子字符串
+        /// <para>如果start大于字符串长度或者length等于0则返回空字符串。</para>
+        /// <para>如果length小于0则返回start前面长度的字符串。</para>
+        /// <para>如果字符串不满足需要的长度要求则返回实际长度字符串。</para>
+        /// <para>如果start小于0，则返回从0开始的length+start长度字符串。</para>
+        /// </summary>
+        /// <param name="str">要检索的字符串</param>
+        /// <param name="start">开始位置</param>
+        /// <param name="length">获取长度</param>
+        /// <returns>子字符串</returns>
+        /// <exception cref="Exception">获取长度不满足要求</exception>
+        public static string SubstringEx(this string str,int start,int length) {
+            if(start > str.Length || length == 0) {
+                return "";
+            }
+            if(length < 0) {
+                start = start + length;
+                length = -length;
+            }
+            if(start < 0) {
+                length += start;
+                start = 0;
+            }
+            if(start + length > str.Length) {
+                return str.Substring(start);
+            }
+            return str.Substring(start,length);
+        }
+
+        /// <summary>
+        /// 按照固定长度分割字符串
+        /// </summary>
+        /// <param name="str">要分割的字符串</param>
+        /// <param name="length">分割长度</param>
+        /// <returns>分割后的字符串枚举</returns>
+        public static IEnumerable<string> Split(this string str,int length) {
+            if(length <= 0) {
+                throw new Exception("分割长度必须大于0");
+            }
+            if(str.IsNullOrEmpty()) {
+                throw new ArgumentNullException(nameof(str));
+            }
+            int i = 0;
+            while(str.Length > i) {
+                yield return str.SubstringEx(i,length);
+                i += length;
+            }
+        }
     }
 }