Get SharePoint list item by List Unique Field using CAML Query

// Function to get value
public SPListItem GetRKListItemByRefNo(SPWeb objSPWeb, string refNo)
    {
        SPList objSPInvoiceList = objSPWeb.Lists["RKList"];
        string camlQuery = string.Empty;
        if (!String.IsNullOrEmpty(refNo))
        {
            camlQuery = "<View><Query><Where><Eq><FieldRef Name='RefNo' /><Value Type='Text'>" + refNo + "</Value></Eq></Where></Query></View>";
        }
        SPQuery qryInv = new SPQuery();
        qryInv.ViewXml = camlQuery;
        SPListItemCollection incAnaCol = objSPInvoiceList.GetItems(qryInv);
        return incAnaCol[0];
    }
    // Calling the function
SPListItem item = GetRKListItemByRefNo(web, itemRefNo);