Dynamic Column Updates in EF Core Without Hand-Rolling SQL Injection

Sometimes you genuinely need the set of columns to update to be data, not code. An operator maps configuration fields to database columns, and you want to honor that mapping without redeploying every time it changes. The naive solution — build an UPDATE string from those column names — is also one of the easiest ways to hand-write a SQL injection vulnerability. This is how to get the flexibility without the hole. We'll build it up in three layers: make it work, make it safe, then count the cost. Layer 1: The dynamic update, the wrong way The tempting version concatenates column names into SQL: // DO NOT do this. var sql = $"UPDATE products SET { columnName } = { value } WHERE id = { id } " ; If columnName comes from configuration that an operator can edit, you've just made your schema writable by whoever controls that config. A value of name = 'x'; DROP TABLE products; -- is now your problem. Even "trusted" config is an injection surface the moment it flows into a SQL string. Layer 2: The same feature with EF.Property EF Core's ExecuteUpdateAsync lets you set a property by name without ever building SQL yourself. EF.Property<T> takes the property name as a string, and EF parameterizes the value and validates the property against the model: await db . Products . Where ( p => p . Id == id ) . ExecuteUpdateAsync ( setters => setters . SetProperty ( p => EF . Property < float ?>( p , columnName ), value )); This is already a different security posture: the value is a parameter, not interpolated text, and EF will throw rather than emit SQL if columnName isn't a real mapped property. But "EF will throw" is a runtime backstop, not a policy. We want to reject bad names before they reach the database, fail closed, and control exactly which columns are writable. Layer 3: Reflection as a whitelist The guard is to validate every incoming column name against the entity's actual properties, using reflection, and to keep an explicit blacklist of fields that must never be touched d