diff --git a/Lombiq.ChartJs.Samples/Controllers/SampleController.cs b/Lombiq.ChartJs.Samples/Controllers/SampleController.cs
index 7a8f9b7..1b3a9e1 100644
--- a/Lombiq.ChartJs.Samples/Controllers/SampleController.cs
+++ b/Lombiq.ChartJs.Samples/Controllers/SampleController.cs
@@ -46,17 +46,17 @@ public SampleController(
     public async Task<IActionResult> Balance() =>
         View(new BalanceViewModel
         {
-            Labels = new[] { Labels.Balance },
-            DataSets = new[]
-            {
+            Labels = [Labels.Balance],
+            DataSets =
+            [
                 // You can find more detailed description about dataset here:
                 // https://www.chartjs.org/docs/2.9.4/charts/bar.html#dataset-properties
                 new ChartJsDataSet
                 {
                     Label = Labels.Incomes,
-                    BackgroundColor = new[] { ChartColors.IncomesBarChartBackgroundColor },
-                    Data = new double?[]
-                    {
+                    BackgroundColor = [ChartColors.IncomesBarChartBackgroundColor],
+                    Data =
+                    [
                         (await _session.QueryIndex<NumericFieldIndex>(
                             index =>
                                 index.Published &&
@@ -68,14 +68,14 @@ public async Task<IActionResult> Balance() =>
                             .ListAsync())
                         .Select(index => decimal.ToDouble(index.Numeric ?? 0m))
                         .Sum(),
-                    },
+                    ],
                 },
                 new ChartJsDataSet
                 {
                     Label = Labels.Expenses,
-                    BackgroundColor = new[] { ChartColors.ExpensesBarChartBackgroundColor },
-                    Data = new double?[]
-                    {
+                    BackgroundColor = [ChartColors.ExpensesBarChartBackgroundColor],
+                    Data =
+                    [
                         (await _session.QueryIndex<NumericFieldIndex>(
                             index =>
                                 index.Published &&
@@ -87,9 +87,9 @@ public async Task<IActionResult> Balance() =>
                             .ListAsync())
                         .Select(index => decimal.ToDouble(index.Numeric ?? 0m))
                         .Sum(),
-                    },
+                    ],
                 },
-            },
+            ],
             Options = new
             {
                 // These options below are to simplify UI testing.
@@ -114,6 +114,8 @@ public async Task<IActionResult> Balance() =>
     // /Lombiq.ChartJs.Samples/Sample/History
     public async Task<IActionResult> History(string incomeTag = null, string expenseTag = null)
     {
+        if (!ModelState.IsValid) return BadRequest(ModelState);
+
         var transactions = await GetMonthlyTransactionsAsync(incomeTag, expenseTag);
 
         return View(new HistoryViewModel
@@ -123,13 +125,13 @@ public async Task<IActionResult> History(string incomeTag = null, string expense
                 .Select(item => item.ToString("MMMM yyyy", CultureInfo.InvariantCulture)),
             // You can find more detailed description about dataset here:
             // https://www.chartjs.org/docs/2.9.4/charts/line.html#dataset-properties
-            DataSets = new[]
-            {
+            DataSets =
+            [
                 new ChartJsDataSet
                 {
                     Label = Labels.Incomes,
-                    BackgroundColor = new[] { ChartColors.Transparent },
-                    BorderColor = new[] { ChartColors.IncomesLineChartBorderColor },
+                    BackgroundColor = [ChartColors.Transparent],
+                    BorderColor = [ChartColors.IncomesLineChartBorderColor],
                     Data = transactions
                         .OrderBy(item => item.Key)
                         .Select(item => item.Value.Income),
@@ -137,13 +139,13 @@ public async Task<IActionResult> History(string incomeTag = null, string expense
                 new ChartJsDataSet
                 {
                     Label = Labels.Expenses,
-                    BackgroundColor = new[] { ChartColors.Transparent },
-                    BorderColor = new[] { ChartColors.ExpensesLineChartBorderColor },
+                    BackgroundColor = [ChartColors.Transparent],
+                    BorderColor = [ChartColors.ExpensesLineChartBorderColor],
                     Data = transactions
                         .OrderBy(item => item.Key)
                         .Select(item => item.Value.Expense),
                 },
-            },
+            ],
             Options = new
             {
                 // These options below are to simplify UI testing.
@@ -203,7 +205,7 @@ await FindDateFieldIndexesByTagsFilterAsync(incomeTag, incomeTagsFilter, expense
 
     private async Task<IEnumerable<string>> GetItemIdsByTermIdAsync(string taxonomyId, string termId) =>
         string.IsNullOrEmpty(termId)
-            ? Array.Empty<string>()
+            ? []
             : (await _orchardHelper.QueryCategorizedContentItemsAsync(query => query
                 .Where(taxIndex => taxIndex.TaxonomyContentItemId == taxonomyId)
                 .Where(taxIndex => taxIndex.TermContentItemId == termId)))
diff --git a/Lombiq.ChartJs/TagHelpers/ChartTagHelper.cs b/Lombiq.ChartJs/TagHelpers/ChartTagHelper.cs
index 1e4789b..ef5e90a 100644
--- a/Lombiq.ChartJs/TagHelpers/ChartTagHelper.cs
+++ b/Lombiq.ChartJs/TagHelpers/ChartTagHelper.cs
@@ -1,7 +1,6 @@
 using Lombiq.ChartJs.Models;
 using Microsoft.AspNetCore.Razor.TagHelpers;
 using OrchardCore.DisplayManagement;
-using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 
@@ -17,10 +16,10 @@ public class ChartTagHelper : TagHelper
     public string ChartType { get; set; } = "bar";
 
     [HtmlAttributeName("labels")]
-    public IEnumerable<string> Labels { get; set; } = Array.Empty<string>();
+    public IEnumerable<string> Labels { get; set; } = [];
 
     [HtmlAttributeName("datasets")]
-    public IEnumerable<ChartJsDataSet> DataSets { get; set; } = Array.Empty<ChartJsDataSet>();
+    public IEnumerable<ChartJsDataSet> DataSets { get; set; } = [];
 
     [HtmlAttributeName("options")]
     public object Options { get; set; } = new();