diff --git a/src/Directory.Build.props b/src/Directory.Build.props
index 330c692..c89c9bc 100644
--- a/src/Directory.Build.props
+++ b/src/Directory.Build.props
@@ -38,6 +38,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="AssemblyMetadata.Generators" Version="2.0.0" PrivateAssets="All" />
     <PackageReference Include="MinVer" Version="5.0.0" PrivateAssets="All" />
   </ItemGroup>
 
@@ -53,5 +54,5 @@
       <Visible>false</Visible>
     </None>
   </ItemGroup>
-  
+
 </Project>
diff --git a/src/FluentRest/FluentDispatcher.cs b/src/FluentRest/FluentDispatcher.cs
index b290b82..337084b 100644
--- a/src/FluentRest/FluentDispatcher.cs
+++ b/src/FluentRest/FluentDispatcher.cs
@@ -52,7 +52,7 @@ private static async Task<HttpRequestMessage> PrepareRequest(HttpRequestMessage
         if (requestMessage.Headers.UserAgent.Count == 0)
         {
             // user-agent header required
-            var headerValue = new ProductInfoHeaderValue("FluentRest", "5.0.0.0");
+            var headerValue = new ProductInfoHeaderValue("FluentRest", ThisAssembly.FileVersion);
             requestMessage.Headers.UserAgent.Add(headerValue);
         }
 
diff --git a/src/FluentRest/StringBuilderCache.cs b/src/FluentRest/StringBuilderCache.cs
new file mode 100644
index 0000000..27c2724
--- /dev/null
+++ b/src/FluentRest/StringBuilderCache.cs
@@ -0,0 +1,54 @@
+using System.Text;
+
+namespace FluentRest;
+
+/// <summary>Provide a cached reusable instance of StringBuilder per thread.</summary>
+internal static class StringBuilderCache
+{
+    // The value 360 was chosen in discussion with performance experts as a compromise between using
+    // as little memory per thread as possible and still covering a large part of short-lived
+    // StringBuilder creations on the startup path of VS designers.
+    internal const int MaxBuilderSize = 360;
+    private const int DefaultCapacity = 16; // == StringBuilder.DefaultCapacity
+
+    [ThreadStatic]
+    private static StringBuilder t_cachedInstance;
+
+    /// <summary>Get a StringBuilder for the specified capacity.</summary>
+    /// <remarks>If a StringBuilder of an appropriate size is cached, it will be returned and the cache emptied.</remarks>
+    public static StringBuilder Acquire(int capacity = DefaultCapacity)
+    {
+        if (capacity > MaxBuilderSize)
+            return new StringBuilder(capacity);
+
+        var sb = t_cachedInstance;
+        if (sb == null)
+            return new StringBuilder(capacity);
+
+        // Avoid StringBuilder block fragmentation by getting a new StringBuilder
+        // when the requested size is larger than the current capacity
+        if (capacity > sb.Capacity)
+            return new StringBuilder(capacity);
+
+        t_cachedInstance = null;
+        sb.Clear();
+
+        return sb;
+
+    }
+
+    /// <summary>Place the specified builder in the cache if it is not too big.</summary>
+    public static void Release(StringBuilder sb)
+    {
+        if (sb.Capacity <= MaxBuilderSize)
+            t_cachedInstance = sb;
+    }
+
+    /// <summary>Release StringBuilder to the cache, and return the resulting string.</summary>
+    public static string ToString(StringBuilder sb)
+    {
+        string result = sb.ToString();
+        Release(sb);
+        return result;
+    }
+}
diff --git a/src/FluentRest/UrlBuilder.cs b/src/FluentRest/UrlBuilder.cs
index 793f257..4279366 100644
--- a/src/FluentRest/UrlBuilder.cs
+++ b/src/FluentRest/UrlBuilder.cs
@@ -544,7 +544,7 @@ public Uri ToUri()
     /// </returns>
     public override string ToString()
     {
-        var builder = new StringBuilder();
+        var builder = StringBuilderCache.Acquire(150);
 
         if (!string.IsNullOrWhiteSpace(_scheme))
             builder.Append(_scheme).Append(_schemeDelimiter);
@@ -553,16 +553,16 @@ public override string ToString()
         {
             builder.Append(_username);
             if (!string.IsNullOrWhiteSpace(_password))
-                builder.Append(":").Append(_password);
+                builder.Append(':').Append(_password);
 
-            builder.Append("@");
+            builder.Append('@');
         }
 
         if (!string.IsNullOrWhiteSpace(_host))
         {
             builder.Append(_host);
             if (_port.HasValue && !IsStandardPort())
-                builder.Append(":").Append(_port);
+                builder.Append(':').Append(_port);
         }
 
         WritePath(builder);
@@ -571,7 +571,7 @@ public override string ToString()
         if (!string.IsNullOrWhiteSpace(_fragment))
             builder.Append(_fragment);
 
-        return builder.ToString();
+        return StringBuilderCache.ToString(builder);
     }
 
 
@@ -586,7 +586,7 @@ private bool IsStandardPort()
 
     private void WritePath(StringBuilder builder)
     {
-        builder.Append("/");
+        builder.Append('/');
         if (Path == null || Path.Count == 0)
             return;
 
@@ -594,12 +594,11 @@ private void WritePath(StringBuilder builder)
         foreach (var p in Path)
         {
             if (builder.Length > start)
-                builder.Append("/");
+                builder.Append('/');
 
-            var s = p.Replace(" ", "+");
-            s = Uri.EscapeUriString(s);
+            var v = Uri.EscapeDataString(p);
 
-            builder.Append(s);
+            builder.Append(v);
         }
     }
 
@@ -608,29 +607,27 @@ private void WriteQueryString(StringBuilder builder)
         if (Query == null || Query.Count == 0)
             return;
 
-        builder.Append("?");
+        builder.Append('?');
 
         int start = builder.Length;
         foreach (var pair in Query)
         {
             var key = pair.Key;
             key = Uri.EscapeDataString(key);
-            key = key.Replace("%20", "+");
 
             var values = pair.Value.ToList();
 
             foreach (var value in values)
             {
                 if (builder.Length > start)
-                    builder.Append("&");
+                    builder.Append('&');
 
                 var v = value;
                 v = Uri.EscapeDataString(v);
-                v = v.Replace("%20", "+");
 
                 builder
                     .Append(key)
-                    .Append("=")
+                    .Append('=')
                     .Append(v);
             }
         }
@@ -763,6 +760,3 @@ private void ParsePath(string s)
     }
 
 }
-
-
-
diff --git a/test/FluentRest.Tests/UrlBuilderTests.cs b/test/FluentRest.Tests/UrlBuilderTests.cs
index db769c3..6e767c1 100644
--- a/test/FluentRest.Tests/UrlBuilderTests.cs
+++ b/test/FluentRest.Tests/UrlBuilderTests.cs
@@ -21,10 +21,10 @@ public UrlBuilderTests(ITestOutputHelper output)
 
     [Theory]
     [InlineData("http://foo/bar/baz", "date", "today", "http://foo/bar/baz?date=today")]
-    [InlineData("http://foo/bar/baz", "date", "sunday afternoon", "http://foo/bar/baz?date=sunday+afternoon")]
+    [InlineData("http://foo/bar/baz", "date", "sunday afternoon", "http://foo/bar/baz?date=sunday%20afternoon")]
     [InlineData("http://foo/bar/baz?date=today", "key1", "value1", "http://foo/bar/baz?date=today&key1=value1")]
-    [InlineData("http://foo/bar/baz?date=today", "key1", "value 1&", "http://foo/bar/baz?date=today&key1=value+1%26")]
-    [InlineData("foo/bar/baz?date=today", "key1", "value 1&", "http://foo/bar/baz?date=today&key1=value+1%26")]
+    [InlineData("http://foo/bar/baz?date=today", "key1", "value 1&", "http://foo/bar/baz?date=today&key1=value%201%26")]
+    [InlineData("foo/bar/baz?date=today", "key1", "value 1&", "http://foo/bar/baz?date=today&key1=value%201%26")]
     public void AppendQuery(string url, string key, string value, string expected)
     {
         var builder = new UrlBuilder(url);