Retrieve all records when SelectCommand.Parameters[].Value is null

hi every body
I have a SelectCommand and i use code below to set it value

Code:

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DataAdapter.SelectCommand.Parameters["@code"].Value = str_code;

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and i defin the parameters with code:

Code:

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DataAdapter.SelectCommand.CommandText = "SELECT * FROM Table  where (code= @code)";
            DataAdapter.SelectCommand.Parameters.Add("@code", SqlDbType.NVarChar, 50, "code");

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now i want when str_code is null SelectCommand retrieve all records in database but i dont want to use condition statments becaus i have many parameters and then i have to write about 100 if-then
i need a T-SQL for doing it

thank you all.

You can pass the parameter to a stored procedure and check in there if it is null or 0 then do the Select all, and use a reader to get the results?