SqlParameter does not allows Table name - other op

Question

I got a runtime error saying "Must declare the table variable "@parmTableName". Meaning having table name as sql parameter in the sql-statement is not allowed.

Is there a better option or suggestion than allowing sql injection attack? I don't want to do this C# script for sql statement " DELETE FROM " + tableName + " ";

using(var dbCommand = dbConnection.CreateCommand())
{
   sqlAsk = "";
   sqlAsk += " DELETE FROM @parmTableName ";
   sqlAsk += " WHERE ImportedFlag = 'F' ";

   dbCommand.Parameters.Clear();
   dbCommand.Parameters.AddWithValue("@parmTableName", tableName);

   dbConnection.Open();

   rowAffected = dbCommand.ExecuteNonQuery();
}

Answer 1

As others have already pointed out that you can't use Table Name and Fields in Sql Parameter, one thing that you can try is to escape table name using SqlCommandBuilder, like:

string tableName = "YourTableName";
var builder = new SqlCommandBuilder();
string escapedTableName = builder.QuoteIdentifier(tableName);

using (var dbCommand = dbConnection.CreateCommand())
{
    sqlAsk = "";
    sqlAsk += " DELETE FROM " + escapedTableName; //concatenate here
    sqlAsk += " WHERE ImportedFlag = 'F' "; 

    dbCommand.Parameters.Clear();

    dbConnection.Open();

    rowAffected = dbCommand.ExecuteNonQuery();
}

Answer 2

(sqlAsk is string, right?) if it's right so let's try this:

using(var dbCommand = dbConnection.CreateCommand())
{
   sqlAsk = "";
   sqlAsk += " DELETE FROM <table_name> ";
   sqlAsk += " WHERE ImportedFlag = 'F' ";

   string table_name = "Your table name here";  //<- fill this as u need 
   sqlAsk = sqlAsk.Replace("<table_name>", table_name); // it will replace <table_name> text to string table_name

   dbConnection.Open();

   rowAffected = dbCommand.ExecuteNonQuery();
}

Answer 3

Go for a white list. There can only be a fixed set of possible correct values for the table name anyway - at least, so I'd hope.

If you don't have a white list of table names, you could start with a whitelist of characters - if you restrict it to A-Z, a-z and 0-9 (no punctuation at all) then that should remove a lot of the concern. (Of course that means you don't support tables with odd names... we don't really know your requirements here.)

But no, you can't use parameters for either table or column names - only values. That's typically the case in databases; I don't remember seeing one which did support parameters for that. (I dare say there are some, of course...)