Is there a way to check if a parameter is in stored procedure?
ArrayList pars = new ArrayList();
SqlParameter p;
int tryInt;
for (int i = 0; i < req.QueryString.Count; i++)
{
    key = req.QueryString.AllKeys[i];

    if (int.TryParse(req[key], out tryInt))
    {
        p = new SqlParameter("@" + key, SqlDbType.Int);
        p.Value = tryInt;
        pars.Add(p);
    }
}

@someParameter is not a parameter for procedure some_sproc

if (paramExists("@" + key, "some_sproc") && int.TryParse(req[key], out tryInt))
{
    p = new SqlParameter("@" + key, SqlDbType.Int);
    p.Value = tryInt;
    pars.Add(p);
}

SELECT parameter_name, ordinal_position FROM INFORMATION_SCHEMA.parameters
WHERE SPECIFIC_NAME = 'some_sproc'

using (SqlConnection sqlConn = new SqlConnection(yourConnStr))
using (SqlCommand sqlCmd = new SqlCommand(yourProcedureName, sqlConn))
{
    sqlConn.Open();
    sqlCmd.CommandType = CommandType.StoredProcedure;
    SqlCommandBuilder.DeriveParameters(sqlCmd);
    // now you can check parameters in sqlCmd.Parameters
}