Encode the resource query as it should be.

src/RestSharp/Request/RestRequest.cs

@@ -12,17 +12,17 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-using System.Net;
 using System.Net.Http.Headers;
-using RestSharp.Authenticators;
-using RestSharp.Extensions;
-using RestSharp.Interceptors;
 
 // ReSharper disable ReplaceSubstringWithRangeIndexer
 // ReSharper disable UnusedAutoPropertyAccessor.Global
 
 namespace RestSharp;
 
+using Authenticators;
+using Extensions;
+using Interceptors;
+
 /// <summary>
 /// Container for data used to make requests
 /// </summary>
@@ -53,7 +53,7 @@ public RestRequest(string? resource, Method method = Method.Get) : this() {
         var queryParams = ParseQuery(Resource.Substring(queryStringStart + 1));
         Resource = Resource.Substring(0, queryStringStart);
 
-        foreach (var param in queryParams) this.AddQueryParameter(param.Key, param.Value, false);
+        foreach (var param in queryParams) this.AddQueryParameter(param.Key, param.Value);
 
         return;
 
@@ -84,12 +84,12 @@ public RestRequest(Uri resource, Method method = Method.Get)
     /// Always send a multipart/form-data request - even when no Files are present.
     /// </summary>
     public bool AlwaysMultipartFormData { get; set; }
-    
+
     /// <summary>
     /// Always send a file as request content without multipart/form-data request - even when the request contains only one file parameter
     /// </summary>
     public bool AlwaysSingleFileAsContent { get; set; }
-    
+
     /// <summary>
     /// When set to true, parameter values in a multipart form data requests will be enclosed in
     /// quotation marks. Default is false. Enable it if the remote endpoint requires parameters
@@ -232,7 +232,7 @@ public Func<HttpResponseMessage, RestRequest, RestResponse>? AdvancedResponseWri
             _advancedResponseHandler = value;
         }
     }
-    
+
     /// <summary>
     /// Request-level interceptors. Will be combined with client-level interceptors if set.
     /// </summary>
@@ -255,4 +255,4 @@ public RestRequest RemoveParameter(Parameter parameter) {
     }
 
     internal RestRequest AddFile(FileParameter file) => this.With(x => x._files.Add(file));
-}
+}

test/RestSharp.Tests/UrlBuilderTests.cs

@@ -236,6 +236,16 @@ public void Should_use_ipv6_address() {
         actual.AbsoluteUri.Should().Be("https://[fe80::290:e8ff:fe8b:2537]:8443/api/v1/auth");
     }
 
+    [Fact]
+    public void Should_encode_resource() {
+        const string baseUrl = "https://example.com";
+        const string resource = "resource?param=value with spaces";
+
+        var request = new RestRequest(resource);
+        var uri = new Uri($"{baseUrl}/{resource}");
+        AssertUri(baseUrl, request, uri.AbsoluteUri);
+    }
+
     [Fact]
     public void Should_not_encode_pipe() {
         var request = new RestRequest("resource").AddQueryParameter("ids", "in:001|116", false);