1 files changed, 43 insertions, 0 deletions
diff --git a/FireBase/Query/ParameterQuery.cs b/FireBase/Query/ParameterQuery.cs
new file mode 100644
index 0000000..e3d9717
--- /dev/null
+++ b/FireBase/Query/ParameterQuery.cs
@@ -0,0 +1,43 @@
+namespace Firebase.Database.Query
+{
+    using System;
+
+    /// <summary>
+    /// Represents a parameter in firebase query, e.g. "?data=foo".
+    /// </summary>
+    public abstract class ParameterQuery : FirebaseQuery
+    {
+        private readonly Func<string> parameterFactory;
+        private readonly string separator;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ParameterQuery"/> class.
+        /// </summary>
+        /// <param name="parent"> The parent of this query. </param>
+        /// <param name="parameterFactory"> The parameter. </param>
+        /// <param name="client"> The owning client. </param>
+        protected ParameterQuery(FirebaseQuery parent, Func<string> parameterFactory, FirebaseClient client)
+            : base(parent, client)
+        {
+            this.parameterFactory = parameterFactory;
+            this.separator = (this.Parent is ChildQuery) ? "?" : "&";
+        }
+
+        /// <summary>
+        /// Build the url segment represented by this query. 
+        /// </summary> 
+        /// <param name="child"> The child. </param>
+        /// <returns> The <see cref="string"/>. </returns>
+        protected override string BuildUrlSegment(FirebaseQuery child)
+        {
+            return $"{this.separator}{this.parameterFactory()}={this.BuildUrlParameter(child)}";
+        }
+
+        /// <summary>
+        /// The build url parameter.
+        /// </summary>
+        /// <param name="child"> The child. </param>
+        /// <returns> The <see cref="string"/>. </returns>
+        protected abstract string BuildUrlParameter(FirebaseQuery child);
+    }
+}