diff --git a/wfassoc/src/lowlevel.rs b/wfassoc/src/lowlevel.rs
index 83564ab..2fdd485 100644
--- a/wfassoc/src/lowlevel.rs
+++ b/wfassoc/src/lowlevel.rs
@@ -998,14 +998,50 @@ impl ExtKey {
 
     const NAMEOF_OPEN_WITH_PROGIDS: &str = "OpenWithProgIds";
 
-    pub fn get_open_with_progids(&self, view: View) -> Result<Vec<LosseProgId>, Error> {
-        todo!()
+    pub fn get_open_with_progids(&self, view: View) -> Result<Option<Vec<LosseProgId>>, Error> {
+        let key = self.open_view_for_getter(view)?;
+        // Get OpenWithProgIds subkey
+        let open_with_progids_key = match regext::try_open_subkey_with_flags(
+            &key,
+            regext::blank_path_guard(Self::NAMEOF_OPEN_WITH_PROGIDS)?,
+            PERM_R,
+        )? {
+            Some(key) => key,
+            None => return Ok(None),
+        };
+        // Fetch all sub-values
+        let key_names = regext::get_all_string_subkey_names(&open_with_progids_key)?;
+        // Map the result
+        let progids = key_names
+            .into_iter()
+            .map(|name| LosseProgId::from(name.as_str()))
+            .collect();
+        // Return value
+        Ok(Some(progids))
     }
 
+    ///
+    ///
+    /// If there is no "OpenWithProgIds" subkey, this function return false.
     pub fn is_in_open_with_progids(&self, view: View, pid: &LosseProgId) -> Result<bool, Error> {
-        todo!()
+        let key = self.open_view_for_getter(view)?;
+        // Get OpenWithProgIds subkey
+        let open_with_progids_key = match regext::try_open_subkey_with_flags(
+            &key,
+            regext::blank_path_guard(Self::NAMEOF_OPEN_WITH_PROGIDS)?,
+            PERM_R,
+        )? {
+            Some(key) => key,
+            None => return Ok(false),
+        };
+        // Check whether there is given ProgId
+        Ok(regext::try_get_value::<String, _>(&open_with_progids_key, pid.to_string())?.is_some())
     }
 
+    ///
+    ///
+    /// If there is no "OpenWithProgIds" subkey, this function will create it first,
+    /// then add your given ProgId into it.
     pub fn add_into_open_with_progids(
         &mut self,
         scope: Scope,
@@ -1014,6 +1050,9 @@ impl ExtKey {
         todo!()
     }
 
+    ///
+    ///
+    /// If there is no "OpenWithProgIds" subkey, this function do nothing.
     pub fn remove_from_open_with_progids(
         &mut self,
         scope: Scope,