diff --git a/CSharpMath.Tests/Generic/BiDictionaryTests.cs b/CSharpMath.Tests/Generic/BiDictionaryTests.cs
new file mode 100644
index 000000000..8ab71efb5
--- /dev/null
+++ b/CSharpMath.Tests/Generic/BiDictionaryTests.cs
@@ -0,0 +1,73 @@
+using Xunit;
+
+namespace CSharpMath.Tests.Generic {
+  public class BiDictionaryTests {
+    [Fact]
+    public void TestRemove() {
+      var testBiDictionary = new BiDictionary<int, string> {
+        { 0, "0" },
+        { 1, "1" },
+        { 2, "8" },
+        { 3, "10" }
+      };
+      Assert.Equal(4, testBiDictionary.Firsts.Count);
+      Assert.Equal(4, testBiDictionary.Seconds.Count);
+
+      Assert.True(testBiDictionary.Remove(2, "8"));
+      Assert.False(testBiDictionary.ContainsByFirst(2));
+      Assert.False(testBiDictionary.ContainsBySecond("8"));
+      Assert.Equal(3, testBiDictionary.Firsts.Count);
+      Assert.Equal(3, testBiDictionary.Seconds.Count);
+
+      // Remove with wrong first key
+      Assert.False(testBiDictionary.Remove(4, "10"));
+      Assert.False(testBiDictionary.ContainsByFirst(4));
+      Assert.True(testBiDictionary.ContainsBySecond("10"));
+      Assert.Equal(3, testBiDictionary.Firsts.Count);
+      Assert.Equal(3, testBiDictionary.Seconds.Count);
+
+      // Remove with wrong second key
+      Assert.False(testBiDictionary.Remove(3, "15"));
+      Assert.True(testBiDictionary.ContainsByFirst(3));
+      Assert.False(testBiDictionary.ContainsBySecond("15"));
+      Assert.Equal(3, testBiDictionary.Firsts.Count);
+      Assert.Equal(3, testBiDictionary.Seconds.Count);
+
+      // Remove when both exists but not corresponding to each other
+      Assert.True(testBiDictionary.Remove(0, "1"));
+      Assert.False(testBiDictionary.ContainsByFirst(0));
+      Assert.False(testBiDictionary.ContainsBySecond("1"));
+      Assert.Single(testBiDictionary.Firsts);
+      Assert.Single(testBiDictionary.Seconds);
+    }
+
+    [Fact]
+    public void TestAddOrReplace() {
+      var testBiDictionary = new BiDictionary<int, string>();
+
+      testBiDictionary.AddOrReplace(0, "Value1");
+      Assert.Equal("Value1", testBiDictionary[0]);
+      Assert.Equal(0, testBiDictionary["Value1"]);
+
+      testBiDictionary.AddOrReplace(2, "Value10");
+      Assert.Equal("Value10", testBiDictionary[2]);
+      Assert.Equal(2, testBiDictionary["Value10"]);
+
+      testBiDictionary.AddOrReplace(2, "Value2");
+      Assert.Equal("Value2", testBiDictionary[2]);
+      Assert.Equal(2, testBiDictionary["Value2"]);
+      Assert.Equal(2, testBiDictionary.Firsts.Count);
+      Assert.Equal(2, testBiDictionary.Seconds.Count);
+
+      testBiDictionary.AddOrReplace(3, "Value3");
+      Assert.Equal("Value3", testBiDictionary[3]);
+      Assert.Equal(3, testBiDictionary["Value3"]);
+
+      testBiDictionary.AddOrReplace(10, "Value3");
+      Assert.Equal("Value3", testBiDictionary[10]);
+      Assert.Equal(10, testBiDictionary["Value3"]);
+      Assert.Equal(3, testBiDictionary.Firsts.Count);
+      Assert.Equal(3, testBiDictionary.Seconds.Count);
+    }
+  }
+}
diff --git a/CSharpMath/Generic/BiDictionary.cs b/CSharpMath/Generic/BiDictionary.cs
index 61c671a61..39f3fc05a 100644
--- a/CSharpMath/Generic/BiDictionary.cs
+++ b/CSharpMath/Generic/BiDictionary.cs
@@ -203,6 +203,15 @@ public void Add(TFirst first, TSecond second) {
       secondToFirst.Add(second, first);
     }
 
+    public void AddOrReplace(TFirst first, TSecond second) {
+      if (firstToSecond.ContainsKey(first))
+        RemoveByFirst(first);
+      if (secondToFirst.ContainsKey(second))
+        RemoveBySecond(second);
+      firstToSecond.Add(first, second);
+      secondToFirst.Add(second, first);
+    }
+
     public Dictionary<TFirst, TSecond>.KeyCollection Firsts => firstToSecond.Keys;
 
     public Dictionary<TSecond, TFirst>.KeyCollection Seconds => secondToFirst.Keys;
@@ -229,14 +238,14 @@ IEnumerator<KeyValuePair<TFirst, TSecond>> IEnumerable<KeyValuePair<TFirst, TSec
       firstToSecond.GetEnumerator();
 
     public void Add(KeyValuePair<TFirst, TSecond> item) => Add(item.Key, item.Value);
-
+    public void AddOrReplace(KeyValuePair<TFirst, TSecond> item) => AddOrReplace(item.Key, item.Value);
     public void Clear() {
       firstToSecond.Clear();
       secondToFirst.Clear();
     }
 
-    public bool Contains(TFirst first) => firstToSecond.ContainsKey(first);
-    public bool Contains(TSecond second) => secondToFirst.ContainsKey(second);
+    public bool ContainsByFirst(TFirst first) => firstToSecond.ContainsKey(first);
+    public bool ContainsBySecond(TSecond second) => secondToFirst.ContainsKey(second);
     public bool Contains(KeyValuePair<TFirst, TSecond> pair) =>
       firstToSecond.TryGetValue(pair.Key, out var second) && EqualityComparer<TSecond>.Default.Equals(second, pair.Value);
 
@@ -245,12 +254,22 @@ public void CopyTo(KeyValuePair<TFirst, TSecond>[] array, int arrayIndex) {
         array[arrayIndex++] = pair;
     }
 
-    public bool Remove(TFirst first, TSecond second) =>
-      firstToSecond.Remove(first) && secondToFirst.Remove(second);
-    public bool Remove(KeyValuePair<TFirst, TSecond> pair) =>
-      firstToSecond.Remove(pair.Key) && secondToFirst.Remove(pair.Value);
-    public bool RemoveFirst(TFirst first) => Remove(first, firstToSecond[first]);
-    public bool RemoveSecond(TSecond second) => Remove(secondToFirst[second], second);
+    public bool Remove(TFirst first, TSecond second) {
+      if (TryGetByFirst(first, out var svalue) && TryGetBySecond(second, out var fvalue)) {
+
+        firstToSecond.Remove(first);
+        firstToSecond.Remove(fvalue);
+
+        secondToFirst.Remove(second);
+        secondToFirst.Remove(svalue);
+        return true;
+      }
+      return false;
+    }
+
+    public bool Remove(KeyValuePair<TFirst, TSecond> pair) => Remove(pair.Key, pair.Value);
+    public bool RemoveByFirst(TFirst first) => Remove(first, firstToSecond[first]);
+    public bool RemoveBySecond(TSecond second) => Remove(secondToFirst[second], second);
   }
 
   public class MultiDictionary<TFirst, TSecond> : IEnumerable<KeyValuePair<TFirst, TSecond>> {