How Can I Dynamically Specify Column Names in C# SqlCommand Queries While Preventing SQL Injection?

Dynamic Query Adjustment for Column Names in C# SqlCommand

When attempting to specify column names using parameters in a SqlCommand object, you may encounter an error stating that parameters cannot be used for column names. This limitation poses a challenge when attempting to execute queries where column names may vary.

Problem:

SqlCommand command = new SqlCommand("SELECT @slot FROM Users WHERE name=@name; ");
prikaz.Parameters.AddWithValue("name", name);
prikaz.Parameters.AddWithValue("slot", slot);

The above code attempts to execute a query with dynamic column names usingparameters, but it fails with the aforementioned error. A potential workaround suggested is the use of stored procedures (SPs) with variable declarations for column names. However, this approach can beumbersome.

Solution:

Instead of parameterizing the column name, you can build the query dynamically at runtime. To ensure security, you should whitelist the input to prevent injection attacks. Here's an example of how you can achieve this:

// TODO: verify that "slot" is an approved/expected value
SqlCommand command = new SqlCommand("SELECT [" + slot + "] FROM Users WHERE name=@name; ")
prikaz.Parameters.AddWithValue("name", name);

In this code, the value of "slot" is used to build the query string during runtime. The parameter "name" is still specified using a parameter to prevent SQL injection. By dynamically constructing the query, you can overcome the limitation of using parameters for column names in SqlCommand.

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