C# code to add Columns/Fields Programmatically to a SharePoint 2010 List

Lets use SharePoint object API to create columns programmatically within an existing List

using (SPSite oSPsite = new SPSite("http://..../Web_URL"))

{

    oSPsite.AllowUnsafeUpdates = true;

    using (SPWeb oSPWeb = oSPsite.OpenWeb())

    {

        oSPWeb.AllowUnsafeUpdates = true;

        /* get the SPList object by list name*/

        SPList lst = oSPWeb.Lists["ListNameHere"];

        /* create a Numeric field for EmpID */

        SPFieldNumber fldEmpID = (SPFieldNumber)lst.Fields.CreateNewField(

                        SPFieldType.Number.ToString(), "EmpID");

        fldEmpID.Required = true;

        fldEmpID.DisplayFormat = SPNumberFormatTypes.NoDecimal;

        /* create a Text field for Name */

        SPFieldText fldName = (SPFieldText)lst.Fields.CreateNewField(

                        SPFieldType.Text.ToString(), "Name");

        fldName.Required = true;

        fldName.MaxLength = 50;

        /* create a Date field for Dob*/

        SPFieldDateTime fldDob = (SPFieldDateTime)lst.Fields.CreateNewField(

                        SPFieldType.DateTime.ToString(), "Dob");

        fldDob.DisplayFormat = SPDateTimeFieldFormatType.DateOnly;

        /* create a Currency field for Salary */

        SPFieldCurrency fldSal = (SPFieldCurrency)lst.Fields.CreateNewField(

                        SPFieldType.Currency.ToString(), "Salary");

        fldSal.Currency = SPCurrencyFieldFormats.UnitedStates;

        fldSal.DisplayFormat = SPNumberFormatTypes.TwoDecimals;

        /* add the new fields to the list */

        lst.Fields.Add(fldEmpID);

        lst.Fields.Add(fldName);

        lst.Fields.Add(fldDob);

        lst.Fields.Add(fldSal);

                   

        /* finally update list */

        lst.Update();

        oSPWeb.AllowUnsafeUpdates = false;

    }

    oSPsite.AllowUnsafeUpdates = false;

}