Problem in fetching row

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C#

ASP.NET

Silverlight4

Hello Friends,
I am developing an application simillar to query designer.
I am facing following trouble
When I am execute query on server side it returns all rows if count of rows less than 21,000 but when row count greater than 21,000 it gives following exception exception

"The remote server returned an error: NotFound. "

Following is my code in WCF Service

public List<Dictionary<string, object>> getDataWithPara(string procName, Dictionary<string, object> dictionary)
        {
            List<Dictionary<string, object>> list_ds = new List<Dictionary<string, object>>();
            try
            {
                SqlConnection conn = new SqlConnection(ConfigurationSettings.AppSettings["constr"].ToString());
                SqlCommand cmd = new SqlCommand(procName, conn);
                cmd.CommandType = CommandType.StoredProcedure;
                conn.Open();
                SqlCommandBuilder.DeriveParameters(cmd);
                foreach (SqlParameter p in cmd.Parameters)
                {
                    if (p.ParameterName.ToLower() != "@return_value")
                    {
                        var val = dictionary.Where(n => n.Key == p.ParameterName).Select(n => n.Value).ToList();
                        p.Value = val[0];
                    }
                }

                DataSet ds = new DataSet();
                SqlDataAdapter sql_da = new SqlDataAdapter(cmd);
                sql_da.Fill(ds);


                Dictionary<string, object> Dct = new Dictionary<string, object>();
                foreach (DataRow dr in ds.Tables[0].Rows)
                {
                    Dct = new Dictionary<string, object>();
                    foreach (DataColumn dc in ds.Tables[0].Columns)
                    {
                        Dct.Add(dc.ColumnName, dr[dc.ColumnName].ToString());
                    }
                    list_ds.Add(Dct);
                }
                Thread.Sleep(1000);
            }
            catch (Exception ex)
            {
                throw new Exception("Error : " + ex.Message);
            }
            finally
            {

            }
            return list_ds;
        }

This is my App.config of wcf application

<system.serviceModel>
    <bindings>
      <basicHttpBinding>
        <binding name="BasicHttpBinding_svc_CRUD"
                 maxBufferSize="2147483647" maxReceivedMessageSize="2147483647"
                 receiveTimeout="00:40:00" openTimeout="00:40:00"
                 closeTimeout="00:40:00" sendTimeout="00:40:00">
          <readerQuotas maxDepth="2147483647"
              maxStringContentLength="2147483647" maxArrayLength="2147483647"
              maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647"/>
          <security mode="None"/>
        </binding>
      </basicHttpBinding>
    </bindings>
		<behaviors>
			<serviceBehaviors>
				<behavior>
					<!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment -->
					<serviceMetadata httpGetEnabled="true" />
          <dataContractSerializer maxItemsInObjectGraph="2147483647" ignoreExtensionDataObject="true"/>
					<!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->
					<serviceDebug includeExceptionDetailInFaults="false" />
				</behavior>
			</serviceBehaviors>
		</behaviors>
		<serviceHostingEnvironment multipleSiteBindingsEnabled="true" aspNetCompatibilityEnabled="true" />
		<services>
   <service name="wcfsvc_master.Session">
    <endpoint address="" binding="basicHttpBinding" contract="wcfsvc_master.ISession" />
    <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
   </service>
      
   <service name="wcfsvc_master.svc_CRUD">
     <endpoint address="" binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_svc_CRUD"
     contract="wcfsvc_master.Isvc_CRUD" />
    <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
    <host>
     <timeouts closeTimeout="00:15:00" openTimeout="00:10:00" />
    </host>
   </service>
  </services>
    <client>
      <endpoint address="" binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_svc_CRUD"
     contract="wcfsvc_master.Isvc_CRUD" />
    </client>
	</system.serviceModel>

Please tell me what i am do