Tutorials ADO.NET Core Tutorial
SQL Injection Prevention — Complete Guide
SQL Injection Prevention — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ADO.NET Core Tutorial on Toolliyo Academy.
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ADO.NET Core Tutorial · Lesson 18 of 100
SQL Injection Prevention
Foundations → SQL & safety → Production → Projects
Foundations · 1 — Connections & CRUD · ~6 min · Module 2: CRUD Operations
What is this?
Prevent injection with parameters, least-privilege DB users, and never building SQL from raw user text.
Why should you care?
One ShopNest breach via injection destroys trust overnight.
See it live — copy this example
Use a .NET console or API project with SQL Server LocalDB. Run dotnet run after pasting.
// allow-list dynamic sort
var sort = col == "Total" ? "Total" : "Id";
cmd.CommandText = $"SELECT Id, Total FROM Orders ORDER BY {sort} DESC"; // sort is allow-listed only
cmd.Parameters.Add("@CustomerId", SqlDbType.Int).Value = customerId;
cmd.CommandText = "SELECT Id, Total FROM Orders WHERE CustomerId=@CustomerId ORDER BY " + sort + " DESC";What happened?
- Values → parameters.
- Identifiers (order by column) → allow-lists.
- Disable xp_cmdshell fantasies; use least privilege.
Practice next
- Allow-list ORDER BY columns.
- Parameterize all values.
- App login without ddl_admin.
- Safe LIKE with @term = '%' + input + '%' via parameter.
- Deny DROP rights to app user.
Remember
Parameters + allow-lists. Least privilege. Defense in depth.
ShopNest hardened data user
App login is db_datareader/writer only.
Outcome: Injection cannot drop tables.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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