Is it possible to pass multiple values to a whereparameter in dynamic datasource

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C#

ASP.NET

I am trying to filter a gridview to show all the records within a date range i.e. greater than equal to from date -and less than equal to todate, using whereParameter on the datasource. As whereParameters by default search with equality and doesnot support >= or <=, I am at a loss how to achieve this. I have tried doing so in the following manner Fig 1. But ended up with the given error Fig2 when the variable dates has more than one value.

Fig 1.

var dates=from t1 in db.tablename
                   where (t1.datecol) >= Convert.ToDateTime(txtDate1.Text)
                   &&  (t1.datecol) >= Convert.ToDateTime(txtDate2.Text)
                   select t1.datecol;

         foreach (var items in dates)
         {
             DateTime EmailDt = Convert.ToDateTime(items);
             string EmailDate = EmailDt.ToString("MM/dd/yyyy");


             string date = Convert.ToString(EmailDate);
	     String value2 = date;
             String name2 = "Approved";
             var param2 = new Parameter();
             param2.Name = name2;
             var fkColumn = table.GetColumn(name2);
             param2.Type = Type.GetTypeCode(fkColumn.ColumnType);
             param2.DefaultValue = value2;
             GridDataSource.WhereParameters.Add(param2);
             GridDataSource.AutoGenerateWhereClause = true;
         }

Fig 2.

Microsoft JScript runtime error: Sys.WebForms.PageRequestManagerServerErrorException: No property or field 'datecol1' exists in type 'tablename'.

Please advise if multivalue is possible or only one value can passed to this whereparameter. Thanx in advance.