Added string.ReplaceFirst extension method.

framework/src/Volo.Abp.Core/System/AbpStringExtensions.cs

@@ -192,6 +192,19 @@ namespace System
             return str;
         }
 
+        public static string ReplaceFirst(this string str, string search, string replace, StringComparison comparisonType = StringComparison.Ordinal)
+        {
+            Check.NotNull(str, nameof(str));
+
+            var pos = str.IndexOf(search, comparisonType);
+            if (pos < 0)
+            {
+                return str;
+            }
+
+            return str.Substring(0, pos) + replace + str.Substring(pos + search.Length);
+        }
+
         /// <summary>
         /// Gets a substring of a string from end of the string.
         /// </summary>

framework/test/Volo.Abp.Core.Tests/System/StringExtensions_Tests.cs

@@ -187,6 +187,14 @@ namespace System
             "Https://abp.io".RemovePreFix(StringComparison.OrdinalIgnoreCase, "https://").ShouldBe("abp.io");
         }
 
+        [Fact]
+        public void ReplaceFirst_Tests()
+        {
+            "Test string".ReplaceFirst("s", "X").ShouldBe("TeXt string");
+            "Test test test".ReplaceFirst("test", "XX").ShouldBe("Test XX test");
+            "Test test test".ReplaceFirst("test", "XX", StringComparison.OrdinalIgnoreCase).ShouldBe("XX test test");
+        }
+
         [Fact]
         public void ToEnum_Test()
         {