Q:

how to convert list object to list string( getting error Unable to cast object of type)

Hi Friends i have a list of objects private static List<Transaction> transactions;
i am querying through the list to filter the data with some criteria. but i am not able to return the list string. i am getting the error

Unable to cast object of type
  <>f__AnonymousType1`6[System.Int32,System.String,System.String,System.String,System.String,System.String]
  to type 'System.String'.

my plan is to make the datagridview source this list like dataGridView2.DataSource = BasicClass.banksearch("ABC");
public static List<string> banksearch(string bankname, string sdate = null, string edate = null, string condition = null)
    {
        List<string> returnstr = new List<string>();
        if (sdate == null && edate == null)//only bank
        {
            returnstr = transactions
                .Where(t => t.BankName == bankname)
                .Select(t => new
                 {
                     TransactionID = t.TransactionID,
                     BankName = t.BankName,
                     TemplateModel = t.TemplateModel,
                     Date = t.Date.ToString(),
                     PayeeName = t.PayeeName,
                     Amount = t.Amount.ToString()
                 }).Cast<String>().ToList();
        }
       return returnstr;
       }

my class file is 
class Transaction
{
        public int TransactionID { get; set; }
        public string BankName { get; set; }
        public string TemplateModel { get; set; }
        public DateTime Date { get; set; }
        public string PayeeName { get; set; }
        public decimal Amount { get; set; }        
}

Please give me idea to get the result

A:

There is no need to project the entire collection onto an Anonymous Object.
All you're actually doing is filtering by bankname:
public static List<Transaction> BankSearch(string bankname, string sdate = null, string edate = null, string condition = null)
{
    List<Transaction> filteredTransactions = new List<Transaction>();
    if (sdate == null && edate == null)
    {
        filteredTransactions = transactions.Where(t => t.BankName == bankname).ToList();
    }

    return filteredTransactions;
}

A:

You don't need to convert to a string in order to use this result as a datasource (although if you actually need a string I can show you how to create a formatted string instead of an anonymous class object). You likely need something like this:
public static List<Transaction> banksearch(string bankname, string sdate = null, string edate = null, string condition = null)
    {
        if (sdate == null && edate == null)//only bank
        {
           return transactions // type: List<Transaction>
                .Where(t => t.BankName == bankname)
                .ToList();
        } else {
           return new List<Transaction>();
       }
  }

