Guard that the name of a property can not be null or empty.

Make sure that Equals and GetHashCode can handle a null value.


Former-commit-id: 8a982497a7ec7182a34d41c44d9dc6658ce4de7c
Former-commit-id: 7c973c93aca38357e5e2b35cebeac9c10c93296b
Former-commit-id: ed06603bf43c266c6619bf81c3a65393f2bf4b2e

src/ImageProcessorCore/Image/ImageProperty.cs

@@ -21,6 +21,8 @@ namespace ImageProcessorCore
         /// <param name="value">The value of the property.</param>
         public ImageProperty(string name, string value)
         {
+            Guard.NotNullOrEmpty(name, nameof(name));
+
             this.Name = name;
             this.Value = value;
         }
@@ -92,12 +94,7 @@ namespace ImageProcessorCore
         {
             ImageProperty other = obj as ImageProperty;
 
-            if (other == null)
-            {
-                return false;
-            }
-
-            return other.Name == this.Name && other.Value == this.Value;
+            return Equals(other);
         }
 
         /// <summary>
@@ -111,7 +108,11 @@ namespace ImageProcessorCore
             unchecked
             {
                 int hashCode = this.Name.GetHashCode();
-                hashCode = (hashCode * 397) ^ this.Value.GetHashCode();
+                if (this.Value != null)
+                {
+                    hashCode = (hashCode * 397) ^ this.Value.GetHashCode();
+                }
+
                 return hashCode;
             }
         }
@@ -146,7 +147,7 @@ namespace ImageProcessorCore
                 return true;
             }
 
-            return this.Name.Equals(other.Name) && this.Value.Equals(other.Value);
+            return this.Name.Equals(other.Name) && Equals(this.Value, other.Value);
         }
     }
 }

tests/ImageProcessorCore.Tests/Image/ImagePropertyTests.cs

@@ -5,6 +5,7 @@
 
 namespace ImageProcessorCore.Tests
 {
+    using System;
     using Xunit;
 
     /// <summary>
@@ -36,6 +37,7 @@ namespace ImageProcessorCore.Tests
             ImageProperty property1 = new ImageProperty("Foo", "Bar");
             ImageProperty property2 = new ImageProperty("Foo", "Foo");
             ImageProperty property3 = new ImageProperty("Bar", "Bar");
+            ImageProperty property4 = new ImageProperty("Foo", null);
 
             Assert.False(property1.Equals("Foo"));
 
@@ -45,8 +47,34 @@ namespace ImageProcessorCore.Tests
             Assert.True(property1 != property2);
 
             Assert.NotEqual(property1, property3);
-            Assert.True(property1 != property3);
+            Assert.NotEqual(property1, property4);
         }
 
+        /// <summary>
+        /// Tests whether the constructor throws an exception when the property name is null or empty.
+        /// </summary>
+        [Fact]
+        public void ConstructorThrowsWhenNameIsNullOrEmpty()
+        {
+            Exception ex = Record.Exception(() => new ImageProperty(null, "Foo"));
+            Assert.IsType<ArgumentNullException>(ex);
+
+            ex = Record.Exception(() => new ImageProperty(string.Empty, "Foo"));
+            Assert.IsType<ArgumentException>(ex);
+        }
+
+        /// <summary>
+        /// Tests whether the constructor correctly assigns properties.
+        /// </summary>
+        [Fact]
+        public void ConstructorAssignsProperties()
+        {
+            ImageProperty property = new ImageProperty("Foo", null);
+            Assert.Equal("Foo", property.Name);
+            Assert.Equal(null, property.Value);
+
+            property = new ImageProperty("Foo", string.Empty);
+            Assert.Equal(string.Empty, property.Value);
+        }
     }
 }