How to Safely Use a List as a SqlParameter for an SQL IN Statement?

Translating a List into a SqlParameter for an SQL IN Statement

Enclosed within the query, an "IN" statement specifies that a specific column must have a matching value within a provided list of values. When working with SQL IN statements utilizing a SqlCommand object, confusion may arise regarding the conversion of a List into a compatible SqlParameter.

In the provided code snippet:

cmd.CommandText = "Select dscr from system_settings where setting in @settings";
cmd.Connection = conn;
cmd.Parameters.Add(new SqlParameter("@settings", settingsList));

reader = cmd.ExecuteReader();

The parameter settingsList represents a List containing the values to be evaluated in the IN statement. However, a direct mapping of the List to a SqlParameter induces an exception due to incompatibility with known provider types.

To safely execute an IN query with SqlCommands, consider employing the following approach:

1. Construct Statement with Placeholders:

string sql = "SELECT dscr FROM system_settings WHERE setting IN ({0})";

In this statement, {0} serves as a placeholder for the dynamic parameter list generated in the next step.

2. Prepare Parameter Array:

string[] paramArray = settingList.Select((x, i) => "@settings" + i).ToArray();

Here, the string array paramArray is derived by iterating through the settingsList and assigning each value to a named parameter of the form "@settings0", "@settings1", etc.

3. Combine Statement with Parameters:

cmd.CommandText = string.Format(sql, string.Join(",", paramArray));

The Format method combines the statement template with the parameter list, resulting in a parameterized SQL statement.

4. Add Parameters:

for (int i = 0; i < settingList.Count; ++i)
{
    cmd.Parameters.Add(new SqlParameter("@settings" + i, settingList[i]));
}

Individual parameters are added to the SqlCommand object using a loop that iterates through the settingsList to ensure that each value has a corresponding parameter.

By following these steps, you can effectively perform an IN query with a SqlCommand object using a List as input while maintaining data security and preventing potential injection attacks.

The above is the detailed content of How to Safely Use a List as a SqlParameter for an SQL IN Statement?. For more information, please follow other related articles on the PHP Chinese website!