Optimize JSON object node.

Core/Collection/List/ListExtensions.cs

@@ -17,6 +17,34 @@ namespace Trivial.Collection;
 /// </summary>
 public static partial class ListExtensions
 {
+    /// <summary>
+    /// Tries to get the string value.
+    /// </summary>
+    /// <param name="dict">The source dictionary.</param>
+    /// <param name="key">The key.</param>
+    /// <param name="value">The value output.</param>
+    /// <returns>true if exist and not empty; otherwise, false.</returns>
+    /// <exception cref="ArgumentNullException">dict or key was null.</exception>
+    public static bool TryGetNotEmptyValue(this IDictionary<string, string> dict, string key, out string value)
+    {
+        if (dict == null) throw new ArgumentNullException(nameof(dict), "dict should not be null.");
+        value = dict.TryGetValue(key, out var v) && !string.IsNullOrEmpty(v) ? v : null;
+        return v != null;
+    }
+
+    /// <summary>
+    /// Tries to get the string value.
+    /// </summary>
+    /// <param name="dict">The source dictionary.</param>
+    /// <param name="key">The key.</param>
+    /// <returns>The value; or null if not exist or empty.</returns>
+    /// <exception cref="ArgumentNullException">dict or key was null.</exception>
+    public static string TryGetNotEmptyValue(this IDictionary<string, string> dict, string key)
+    {
+        if (dict == null) throw new ArgumentNullException(nameof(dict), "dict should not be null.");
+        return dict.TryGetValue(key, out var v) && !string.IsNullOrEmpty(v) ? v : null;
+    }
+
     /// <summary>
     /// Adds a key and a value to the end of the key value pairs.
     /// </summary>

Core/Text/Json/ObjectNode.cs

@@ -1080,6 +1080,21 @@ public IJsonDataNode GetValue(string key)
         return store[key] ?? JsonValues.Null;
     }
 
+    /// <summary>
+    /// Gets the value of the specific property.
+    /// </summary>
+    /// <param name="key">The property key.</param>
+    /// <param name="undefined">true if return undefined when the property does not exist; otherwise, false.</param>
+    /// <returns>The value.</returns>
+    /// <exception cref="ArgumentNullException">The property key should not be null, empty, or consists only of white-space characters.</exception>
+    /// <exception cref="ArgumentOutOfRangeException">The property does not exist and argument undefined is false.</exception>
+    public IJsonDataNode GetValue(string key, bool undefined)
+    {
+        AssertKey(key);
+        if (!undefined) return store[key] ?? JsonValues.Null;
+        return store.TryGetValue(key, out var v) ? (v ?? JsonValues.Null) : JsonValues.Undefined;
+    }
+
     /// <summary>
     /// Gets the value of the specific property.
     /// </summary>