Do not short-circuit tenant resolver chain when query string tenant value is blank

framework/src/Volo.Abp.AspNetCore.MultiTenancy/Volo/Abp/AspNetCore/MultiTenancy/QueryStringTenantResolveContributor.cs

@@ -19,13 +19,10 @@ public class QueryStringTenantResolveContributor : HttpTenantResolveContributorB
             if (httpContext.Request.Query.ContainsKey(tenantKey))
             {
                 var tenantValue = httpContext.Request.Query[tenantKey].ToString();
-                if (tenantValue.IsNullOrWhiteSpace())
+                if (!tenantValue.IsNullOrWhiteSpace())
                 {
-                    context.Handled = true;
+                    return Task.FromResult(tenantValue)!;
-                    return Task.FromResult<string?>(null);
                 }
-
-                return Task.FromResult(tenantValue)!;
             }
         }
 

framework/test/Volo.Abp.AspNetCore.MultiTenancy.Tests/Volo/Abp/AspNetCore/MultiTenancy/AspNetCoreMultiTenancy_Without_DomainResolver_Tests.cs

@@ -70,4 +70,20 @@ public class AspNetCoreMultiTenancy_Without_DomainResolver_Tests : AspNetCoreMul
         var result = await GetResponseAsObjectAsync<Dictionary<string, string>>("http://abp.io");
         result["TenantId"].ShouldBe(_testTenantId.ToString());
     }
+
+    [Fact]
+    public async Task Should_Use_Header_Tenant_Id_When_QueryString_Tenant_Is_Empty()
+    {
+        Client.DefaultRequestHeaders.Add(_options.TenantKey, _testTenantId.ToString());
+
+        var result = await GetResponseAsObjectAsync<Dictionary<string, string>>($"http://abp.io?{_options.TenantKey}=");
+        result["TenantId"].ShouldBe(_testTenantId.ToString());
+    }
+
+    [Fact]
+    public async Task Should_Fallback_To_Host_When_QueryString_Tenant_Is_Empty_And_No_Other_Resolver()
+    {
+        var result = await GetResponseAsObjectAsync<Dictionary<string, string>>($"http://abp.io?{_options.TenantKey}=");
+        result["TenantId"].ShouldBe("");
+    }
 }