diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index c34eab1..7033e22 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -111,4 +111,8 @@
 
 ### **v1.2.0.0** 
 -> Add/adjust input validations in the `DataTypeExtensions` foler with extensions;<br />
--> Add new string extensions: `IfNullThenEmpty`.<br />
\ No newline at end of file
+-> Add new string extensions: `IfNullThenEmpty`.<br />
+
+### **v1.3.0.0** 
+-> Fix test for `CalculateAge`;<br />
+-> Add new string extensions: `IsValidJson`, `IsValidJsonObject`, `IsValidJsonArray`.<br />
\ No newline at end of file
diff --git a/src/DomainCommonExtensions/DataTypeExtensions/StringExtensions.cs b/src/DomainCommonExtensions/DataTypeExtensions/StringExtensions.cs
index 853774b..3af6aa1 100644
--- a/src/DomainCommonExtensions/DataTypeExtensions/StringExtensions.cs
+++ b/src/DomainCommonExtensions/DataTypeExtensions/StringExtensions.cs
@@ -29,6 +29,7 @@
 
 #if NET || NETSTANDARD2_0_OR_GREATER
 using System.Text.Encodings.Web;
+using System.Text.Json;
 #endif
 
 using System.Text.RegularExpressions;
@@ -1373,6 +1374,7 @@ public static string AddQueryString(this string url, string name, string value)
             return url.AddQueryString(name + "=" + UrlEncoder.Default.Encode(value.IfNullThenEmpty()));
         }
 #endif
+
         /// <summary>
         ///     Add hash fragment to URL
         /// </summary>
@@ -1494,5 +1496,83 @@ public static string TrimSuffix(this string source, string suffix, StringCompari
         /// <returns></returns>
         /// <remarks></remarks>
         public static string IfNullThenEmpty(this string source) => source ?? string.Empty;
+
+#if NET || NETSTANDARD2_0_OR_GREATER
+
+        /// <summary>
+        ///     Check if provided source is as valid JSON
+        /// </summary>
+        /// <param name="source">Source string</param>
+        /// <returns></returns>
+        /// <remarks></remarks>
+        public static bool IsValidJson(this string source)
+        {
+            try
+            {
+                if (source.IsMissing()) return false;
+                if ((source.TrimIfNotNull().StartsWith("{") && source.TrimIfNotNull().EndsWith("}")) ||
+                    (source.TrimIfNotNull().StartsWith("[") && source.TrimIfNotNull().EndsWith("]")))
+                {
+                    using var jsonDoc = JsonDocument.Parse(source);
+
+                    return true;
+                }
+                else return false;
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        ///     Check if provided source is as valid JSON object
+        /// </summary>
+        /// <param name="source">Source string</param>
+        /// <returns></returns>
+        /// <remarks></remarks>
+        public static bool IsValidJsonObject(this string source)
+        {
+            try
+            {
+                if (source.IsMissing()) return false;
+                if (source.TrimIfNotNull().StartsWith("{")
+                    && source.TrimIfNotNull().EndsWith("}"))
+                {
+                    return source.IsValidJson();
+                }
+                else return false;
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        ///     Check if provided source is as valid JSON array
+        /// </summary>
+        /// <param name="source">Source string</param>
+        /// <returns></returns>
+        /// <remarks></remarks>
+        public static bool IsValidJsonArray(this string source)
+        {
+            try
+            {
+                if (source.IsMissing()) return false;
+                if (source.TrimIfNotNull().StartsWith("[")
+                    && source.TrimIfNotNull().EndsWith("]"))
+                {
+                    return source.IsValidJson();
+                }
+                else return false;
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
+#endif
     }
 }
\ No newline at end of file
diff --git a/src/DomainCommonExtensions/DomainCommonExtensions.csproj b/src/DomainCommonExtensions/DomainCommonExtensions.csproj
index 34174c1..f80cdbc 100644
--- a/src/DomainCommonExtensions/DomainCommonExtensions.csproj
+++ b/src/DomainCommonExtensions/DomainCommonExtensions.csproj
@@ -61,6 +61,9 @@
     <PackageReference Include="System.Text.Encodings.Web">
       <Version>4.7.2</Version>
     </PackageReference>
+    <PackageReference Include="System.Text.Json">
+      <Version>4.7.2</Version>
+    </PackageReference>
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net45'">
diff --git a/src/shared/GeneralAssemblyInfo.cs b/src/shared/GeneralAssemblyInfo.cs
index e233b4b..2c8f46a 100644
--- a/src/shared/GeneralAssemblyInfo.cs
+++ b/src/shared/GeneralAssemblyInfo.cs
@@ -47,6 +47,6 @@
 [assembly: NeutralResourcesLanguage("en-US", UltimateResourceFallbackLocation.MainAssembly)]
 #endif
 
-[assembly: AssemblyVersion("1.2.0.0")]
-[assembly: AssemblyFileVersion("1.2.0.0")]
-[assembly: AssemblyInformationalVersion("1.2.0.0")]
+[assembly: AssemblyVersion("1.3.0.0")]
+[assembly: AssemblyFileVersion("1.3.0.0")]
+[assembly: AssemblyInformationalVersion("1.3.0.0")]
diff --git a/src/tests/DataTypeTests/DateTimeTests.cs b/src/tests/DataTypeTests/DateTimeTests.cs
index 9764433..f87dfbc 100644
--- a/src/tests/DataTypeTests/DateTimeTests.cs
+++ b/src/tests/DataTypeTests/DateTimeTests.cs
@@ -164,8 +164,12 @@ public void CalculateAgeTest()
             var date = new DateTime(1994, 8, 8, 13, 0, 0);
             var res = date.CalculateAge();
 
+            var age = DateTime.Now.Date.Day >= date.Day
+                ? DateTime.Now.Year - 1994
+                : (DateTime.Now.Year - 1994) + 1;
+
             Assert.IsNotNull(res);
-            Assert.IsTrue(res.Equals(29));
+            Assert.IsTrue(res.Equals(age));
         }
 
         [TestMethod]
diff --git a/src/tests/DataTypeTests/StringTests.cs b/src/tests/DataTypeTests/StringTests.cs
index db7131f..30e9747 100644
--- a/src/tests/DataTypeTests/StringTests.cs
+++ b/src/tests/DataTypeTests/StringTests.cs
@@ -510,5 +510,30 @@ public void ValidatePullTest()
 
             Assert.IsTrue(result);
         }
+
+        [DataRow("{ \"key\": \"value\" }")]
+        [DataRow("[{ \"key\": \"value\" }]")]
+        [DataRow("{ \"key\": 1 }")]
+        [DataRow("[{ \"key\": 1 }]")]
+        [TestMethod]
+        public void IsValidJson_Success_Test(string source)
+        {
+            var result = source.IsValidJson();
+
+            Assert.IsTrue(result);
+        }
+
+        [DataRow("{ \"key\": \"value\"")]
+        [DataRow("{ \"key\": \"value\"")]
+        [DataRow("[{ key: \"value\" }]")]
+        [DataRow("{ \"key\": 1 }]")]
+        [DataRow("\"key\": 1")]
+        [TestMethod]
+        public void IsValidJson_Fail_Test(string source)
+        {
+            var result = source.IsValidJson();
+
+            Assert.IsFalse(result);
+        }
     }
 }
\ No newline at end of file