Why Inspecting methods and properties in C Sharp (C#)? - Purpose & Use Cases

The Big Idea

What if you could instantly see everything an object can do without guessing?

The Scenario

Imagine you have a big toolbox full of different tools, but no labels or instructions. You want to find out what each tool can do, but you have to open each box and guess by looking inside.

The Problem

Manually checking each tool one by one is slow and tiring. You might miss some tools or forget what each one does. It's easy to make mistakes and waste time.

The Solution

Inspecting methods and properties lets you quickly list what each tool (object) can do without opening every box. It's like having a magic list that shows all features instantly.

Before vs After

✗ Before

Console.WriteLine("Tool1: Use it for fixing");
Console.WriteLine("Tool2: Use it for measuring");

✓ After

var methods = typeof(Tool).GetMethods();
foreach(var method in methods) {
  Console.WriteLine(method.Name);
}

What It Enables

This lets you explore and understand any object's abilities easily, making your code smarter and debugging faster.

Real Life Example

When using a new library, inspecting its methods helps you discover what you can do without reading all the documentation first.

Key Takeaways

Manual checking is slow and error-prone.

Inspecting methods and properties gives a quick overview of an object's capabilities.

This helps you write better code and understand new tools faster.

Practice

1. Which C# method is used to get the type information of an object instance?

easy

A. typeof()

B. GetMethods()

C. GetProperties()

D. GetType()

Solution

1. Step 1: Understand the difference between GetType() and typeof()

   GetType() is called on an object instance to get its runtime type, while typeof() is used with a type name at compile time.

2. Step 2: Identify the method that works on an object instance

   Since the question asks for the method used on an object instance, GetType() is the correct choice.

3. Final Answer:

   GetType() -> Option D

4. Quick Check:

   Object instance method for type info = GetType() [OK]

Hint: Use GetType() on objects, typeof() on type names [OK]

Common Mistakes:

• Confusing typeof() with GetType()
• Using GetMethods() to get type info
• Thinking GetProperties() returns type

2. Which of the following is the correct syntax to get all methods of the String type in C#?

easy

A. typeof(String).GetMethods()

B. typeof(String).GetProperties()

C. String.GetMethods()

D. GetType(String).GetMethods()

Solution

1. Step 1: Recall how to get methods from a type

   Use typeof(TypeName).GetMethods() to get all methods of a type.

2. Step 2: Check each option's syntax

   typeof(String).GetMethods() uses typeof(String).GetMethods(), which is correct. typeof(String).GetProperties() calls GetProperties(), not methods. String.GetMethods() tries to call GetMethods() on the type name directly, which is invalid. GetType(String).GetMethods() uses GetType(String), which is incorrect syntax.

3. Final Answer:

   typeof(String).GetMethods() -> Option A

4. Quick Check:

   Get methods from type = typeof(Type).GetMethods() [OK]

Hint: Use typeof(Type).GetMethods() to list methods [OK]

Common Mistakes:

• Calling GetMethods() on type name directly
• Mixing GetProperties() with GetMethods()
• Using GetType() with a type name instead of instance

3. What will the following C# code output?

var props = typeof(DateTime).GetProperties();
Console.WriteLine(props.Length);

medium

A. 0

B. More than 0

C. Compilation error

D. Runtime exception

Solution

1. Step 1: Understand what GetProperties() returns

   GetProperties() returns an array of all public properties of the type.

2. Step 2: Check if DateTime has properties

   DateTime has many properties like Now, Today, Year, Month, etc., so the array length will be more than zero.

3. Final Answer:

   More than 0 -> Option B

4. Quick Check:

   DateTime properties count > 0 [OK]

Hint: Types like DateTime have many properties, so length > 0 [OK]

Common Mistakes:

• Assuming no properties means length 0
• Expecting compilation or runtime errors
• Confusing methods with properties

4. Identify the error in this C# code snippet:

var typeInfo = "hello".GetType();
var methods = typeInfo.GetMethod();

medium

A. GetType() is invalid on string

B. Missing parentheses on GetType

C. GetMethod() should be GetMethods()

D. Cannot call GetMethod() on typeInfo

Solution

1. Step 1: Check usage of GetType()

   "hello".GetType() is valid and returns the type of the string instance.

2. Step 2: Check method name on typeInfo

   There is no method called GetMethod() without parameters; to get all methods, use GetMethods().

3. Final Answer:

   GetMethod() should be GetMethods() -> Option C

4. Quick Check:

   Use GetMethods() to get all methods [OK]

Hint: Use GetMethods() (plural) to list all methods [OK]

Common Mistakes:

• Using GetMethod() without parameters
• Thinking GetType() is invalid on string
• Missing parentheses on method calls

5. You want to list all public properties of a custom class Person and print their names. Which code snippet correctly does this?

hard

A. var props = typeof(Person).GetProperties(); foreach(var p in props) Console.WriteLine(p.Name);

B. var props = new Person().GetProperties(); foreach(var p in props) Console.WriteLine(p.Name);

C. var props = typeof(Person).GetMethods(); foreach(var p in props) Console.WriteLine(p.Name);

D. var props = Person.GetProperties(); foreach(var p in props) Console.WriteLine(p.Name);

Solution

1. Step 1: Identify how to get properties of a type

   Use typeof(Person).GetProperties() to get all public properties of the Person class.

2. Step 2: Check the foreach loop to print property names

   Iterate over the properties and print each p.Name to display property names.

3. Step 3: Verify other options

   var props = new Person().GetProperties(); foreach(var p in props) Console.WriteLine(p.Name); tries to call GetProperties() on an instance, which is invalid. var props = typeof(Person).GetMethods(); foreach(var p in props) Console.WriteLine(p.Name); gets methods, not properties. var props = Person.GetProperties(); foreach(var p in props) Console.WriteLine(p.Name); calls GetProperties() directly on the class name, which is invalid syntax.

4. Final Answer:

   var props = typeof(Person).GetProperties(); foreach(var p in props) Console.WriteLine(p.Name); -> Option A

5. Quick Check:

   Use typeof(Type).GetProperties() and loop to print names [OK]

Hint: Use typeof(Class).GetProperties() and loop to print names [OK]

Common Mistakes:

• Calling GetProperties() on an instance
• Using GetMethods() instead of GetProperties()
• Calling GetProperties() directly on class name