https://csharp-video-tutorials.blogspot.com/2013/08/part-86-validationsummary-in-aspnet-mvc.html
Sql server, .net and c# video tutorial: Part 86 - ValidationSummary in asp.net mvc
Free C#, .NET and SQL Server Video Tutorials for beginners and intermediate programmers.
https://www.w3.org/TR/2012/NOTE-WCAG20-TECHS-20120103/SL35.html
SL35: Using the Validation and ValidationSummary APIs to Implement Client Side Forms Validation in...
https://learn.microsoft.com/ja-jp/previous-versions/windows/silverlight/dotnet-windows-silverlight/dd849985(v=vs.95)
ValidationSummary.Target Property (System.Windows.Controls) | Microsoft Learn
property systemtargetwindowscontrolsmicrosoft
https://learn.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.validationsummary.showsummary?view=netframework-4.8.1&redirectedfrom=MSDN
ValidationSummary.ShowSummary Property (System.Web.UI.WebControls) | Microsoft Learn
Gets or sets a value indicating whether the validation summary is displayed inline.
property systemweb uimicrosoftlearn