title: OPC Client Write item
body: <p>Im making an OPC Client which makes use of the OPC Foundation API DA 3.0 and using a Schneider OFS server.
  I am able to read items from the server that are in a group and I'm also able to write short values to item. </p>
  
  <p>I'm facing difficulties writing a string value to an item and writing a float value to an item.</p>
  
  <p>The item's value won't change.</p>
  
  <p>The float item is named ""DevExample_1!OUTPUT_REAL_VALUE" on the server.</p>
  
  <pre><code>        string[] groupitems = { "Test_device!INPUT_INT_VALUE", "Test_device!OUTPUT_INT_VALUE", "DevExample_1!INPUT_STRING_VALUE","DevExample_1!OUPUT_STRING_VALUE","DevExample_1!OUTPUT_REAL_VALUE"};
          Opc.Da.Subscription group = CreateGroup(server, "GroupTest", groupitems);
  
          WriteGroupItemValue(group, "DevExample_1!OUTPUT_REAL_VALUE", 1.5e-02);
  
      public static Opc.Da.Subscription CreateGroup(Opc.Da.Server server, string groupName, string[] groupitems)
      {
          Opc.Da.SubscriptionState groupState;
          Opc.Da.Subscription groupReadWrite;
  
          groupState = new Opc.Da.SubscriptionState(); // subscr state
          groupState.Name = groupName;
          groupState.UpdateRate = 1000;// this is the time between every reads from OPC server
          groupState.Active = true;//this must be true if you the group has to read value
          groupReadWrite = (Opc.Da.Subscription)server.CreateSubscription(groupState); // add subscr for groupReadWrite
  
          itemsLength = groupitems.Length; // determine amount of items
  
          items = new Opc.Da.Item[itemsLength]; // items array of DA type
  
          for (int i = 0; i &lt; items.Length; i++)
          {
              items[i] = new Opc.Da.Item(); // create new DA item for every index
              items[i].ItemName = groupitems[i];  
          }
          items = groupReadWrite.AddItems(items);
          return groupReadWrite;
      }
  
         public static void WriteGroupItemValue(Opc.Da.Subscription group, string itemName, object itemValue){
  
          Opc.Da.Item[] itemToAddWrite = new Opc.Da.Item[1]; /
          itemToAddWrite[0] = new Opc.Da.Item();
          itemToAddWrite[0].ItemName = itemName;
  
          Opc.Da.ItemValue[] writeValues = new Opc.Da.ItemValue[1];
          writeValues[0] = new Opc.Da.ItemValue(itemToAddWrite[0]);
  
          writeValues[0].Value = itemValue; // set value
  
          writeValues[0].ServerHandle = group.Items[0].ServerHandle;
  
          group.Write(writeValues); // write the value of the items
      }
  </code></pre>