Dynamic caml query in SharePoint

#region Dynamic caml Qeury class

    /// <summary>

    /// Create the class to dynamic CAML Query.

    /// </summary>

    public class CamlQueryElements

    {

        public string LogicalJoin { get; set; } // like <Or>, <And>

        public string ComparisonOperators { get; set; } // like <Eq>, <Contains>

        public string FieldName { get; set; } // Like Title

        public string FieldType { get; set; } // Like Text

        public string FieldValue { get; set; } // some value

    }

    /// <summary>

    /// Class name CamlQuery

    /// </summary>

    public class CamlQuery

    {

        /// <summary>

        /// Passing the Filter field and Filter value in datatable

        /// </summary>

        /// <param name="dtFilterQeury"></param>

        /// <returns></returns>

        public IList<CamlQueryElements> AddElement(DataTable dtFilterQeury)

        {

            IList<CamlQueryElements> lstOfElement = new List<CamlQueryElements>();

            foreach (DataRow dtRow in dtFilterQeury.Rows)

            {

                lstOfElement.Add(new CamlQueryElements

                {

                    ComparisonOperators = "Eq",

                    FieldName = Convert.ToString(dtRow["FilterField"]),

                    FieldType = GetFilterType(Convert.ToString(dtRow["FilterField"])),

                    FieldValue = Convert.ToString(dtRow["FilterValue"]),

                    LogicalJoin = "And"

                });

            }

            return lstOfElement;

        }

        /// <summary>

        /// switch statement to get filterText value

        /// </summary>

        /// <param name="FilterType">column name</param>

        /// <returns></returns>

        public string GetFilterType(string FilterType)

        {

            String FilterText = "Text";

            switch (FilterType)

            {

                case "ID":

                    return FilterText = "Integer";

                case "PriorityLevel":

                    return FilterText = "Text";

                case "AssignTo":

                    return FilterText = "GroupColumn";

                case "ExpectedDueDate":

                    return FilterText = "DateTime";

                case "MatterDefined":

                    return FilterText = "Text";

                case "LinkTitleNoMenu":

                    return FilterText = "Text";

                case "MatterStatus":

                    return FilterText = "Choice";

                default:

                    return FilterText;

            }

        }

        /// <summary>

        /// final funtion of caml Query

        /// </summary>

        /// <param name="dtFilterQeury"></param>

        /// <returns></returns>

        public string GetDynamicQuery(DataTable dtFilterQeury)

        {

            IList<CamlQueryElements> camlIlist = AddElement(dtFilterQeury);

            string dyanmicCamlQuery = GenerateQuery(camlIlist);

            return dyanmicCamlQuery;

        }

        // This function loop List of camlqueryelments which has our filter criteria

        // Then generate query in required format.

        // At end it return string which holds caml query.

        public string GenerateQuery(IList<CamlQueryElements> lstOfElement)

        {

            StringBuilder queryJoin = new StringBuilder();

            string query = @"<{0}><FieldRef Name='{1}' /><Value {2} Type='{3}'>{4}</Value></{5}>";

            if (lstOfElement.Count > 0)

            {

                int itemCount = 0;

                foreach (CamlQueryElements element in lstOfElement)

                {

                    itemCount++;

                    string date = string.Empty;

                    // Display only Date

                    if (String.Compare(element.FieldType, "DateTime", true) == 0)

                        date = "IncludeTimeValue='false'";

                    queryJoin.AppendFormat

                   (string.Format(query, element.ComparisonOperators, element.FieldName,

                       date, element.FieldType, element.FieldValue, element.ComparisonOperators));

                    if (itemCount >= 2)

                    {

                        queryJoin.Insert(0, string.Format("<{0}>", element.LogicalJoin));

                        queryJoin.Append(string.Format("</{0}>", element.LogicalJoin));

                    }

                }

                queryJoin.Insert(0, "<Where>");

                queryJoin.Append("</Where>");

            }

            return queryJoin.ToString();

        }

    }

    #endregion

here are reference url:

http://sharepoint.infoyen.com/2012/03/08/create-dynamic-caml-query-in-sharepoint/