diff --git a/lib/generators.ts b/lib/generators.ts
index 02bdece..8043dff 100644
--- a/lib/generators.ts
+++ b/lib/generators.ts
@@ -68,34 +68,10 @@ export function* DistinctFast<T>(target: Iterable<T>) {
 }
 
 
-export function* OfType<T>(target: Iterable<T>, obj: any) {
-    if (Number === obj) {
+export function* OfType<T>(target: Iterable<T>, obj: any, typeName: string) {
+    if (typeName){
         for (let value of target) {
-            if (Constant.CONST_NUMBER == typeof(value)) {
-                yield value;
-            } else if (value instanceof obj) {
-                yield value;
-            }
-        }
-    } else if (Boolean === obj) {
-        for (let value of target) {
-            if (Constant.CONST_BOOLEAN == typeof(value)) {
-                yield value;
-            } else if (value instanceof obj) {
-                yield value;
-            }
-        }
-    } else if (String === obj) {
-        for (let value of target) {
-            if (Constant.CONST_STRING == typeof(value)) {
-                yield value;
-            } else if (value instanceof obj) {
-                yield value;
-            }
-        }
-    } else if (Symbol === obj) {
-        for (let value of target) {
-            if (Constant.CONST_SYMBOL == typeof(value)) {
+            if (typeName == typeof(value)) {
                 yield value;
             } else if (value instanceof obj) {
                 yield value;
@@ -111,7 +87,8 @@ export function* OfType<T>(target: Iterable<T>, obj: any) {
 }
 
 
-export function* Where<T>(target: Iterable<T>, predicate: (x: T, i: number) => Boolean) {
+export function* Where<T>(target: Iterable<T>, 
+                          predicate: (x: T, i: number) => Boolean) {
     let index = 0;
     for (let value of target) {
         if (!predicate(value, index++)) continue;
diff --git a/lib/linq.ts b/lib/linq.ts
index 46bb28f..c42b0cf 100644
--- a/lib/linq.ts
+++ b/lib/linq.ts
@@ -574,7 +574,29 @@ class EnumerableImpl<T> implements Enumerable<T>, Iterable<T>, IEnumerable<T> {
 
     
     public OfType(obj: any): Enumerable<T> {
-        this._target = Generator.OfType(this._target, obj);
+        let typeName: string;
+        switch (obj) {
+            case Number:
+                typeName = Constant.CONST_NUMBER;
+                break;
+                
+            case Boolean:
+                typeName = Constant.CONST_BOOLEAN;
+                break;
+                
+            case String:
+                typeName = Constant.CONST_STRING;
+                break;
+                
+            case Symbol:
+                typeName = Constant.CONST_SYMBOL;
+                break;
+                
+            default:
+                typeName = undefined;
+        }
+            
+        this._target = Generator.OfType(this._target, obj, typeName);
         return this;
     }