using CMS.CMSHelper;

using CMS.SettingsProvider;

using CMS.SiteProvider;

using CMS.DataEngine;

...

        string customTableClassName = "customtable.SampleTable";

        // Get data class using custom table name

        DataClassInfo customTableClassInfo = DataClassInfoProvider.GetDataClass(customTableClassName);

        // Check if data class info exists

        if (customTableClassInfo != null)

        {

            // Initialize custom table item provider with current user info and general connection

          CustomTableItemProvider ctiProvider = new CustomTableItemProvider(CMSContext.CurrentUser, ConnectionHelper.GetConnection());

            // Provide ID of item you want to delete

            int itemId = 1;

            // Get custom table item with given item ID

            CustomTableItem item = ctiProvider.GetItem(itemId, customTableClassInfo.ClassName);

            // Check if item exists

            if (item != null)

            {

                // Delete item

                item.Delete();

            }

        }