Hi,
I tried to implement the following code as module, but iam unable to get result to my filter dropdown

MY Reference Link

dd_district.info

name = Dropdown District
description = Provides dropdown filter for District field
core = 7.x
files[] = dd_district.module

dd_district.module

function dd_district_form_views_exposed_form_alter(&$form, &$form_state) {
  $field_id = 'field_district'; // change for the field in question

  // Only alter forms with the necessary field
  if (isset($form[$field_id .'_value'])) {
    // Build a query to get all node ids having the specified field
    $query = new EntityFieldQuery();
    $results = $query->entityCondition('entity_type', 'node')
    ->fieldCondition($field_id, 'value', '', '!=')
    ->fieldOrderBy($field_id, 'value', 'ASC')
    ->execute();
     
    // Attach the field values to the nodes
    $nodes = $results['node'];
    field_attach_load('node', $nodes, FIELD_LOAD_CURRENT, array('field_id' => $field_id));

    // Add a default so the filter is optional
    $options = array('' => '---');
     
    // Buld the options array based on the query results, overwriting duplicate entries
    foreach($nodes as $nid => $node) {
      $value = $node->{$field_id}['und'][0]['value'];
      $options[$value] = $value;
    }

    // Alter the field
    $form[$field_id .'_value']['#type'] = 'select';
    $form[$field_id .'_value']['#options'] = $options;
    $form[$field_id .'_value']['#size'] = 1;
  }
}