Inspecting methods and properties in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Inspecting methods and properties

Create object instance

↓

Access type info

↓

Get methods list

↓

Get properties list

↓

Display names and details

↓

End

This flow shows how to create an object, get its type info, then list and display its methods and properties.

Execution Sample

C Sharp (C#)

using System;
using System.Reflection;

var obj = "Hello";
var type = obj.GetType();
var methods = type.GetMethods();
var properties = type.GetProperties();

This code creates a string object, gets its type, then retrieves its methods and properties.

Execution Table

Step	Action	Evaluation	Result
1	Create object instance	obj = "Hello"	obj is a string object with value "Hello"
2	Get type info	type = obj.GetType()	type is System.String type info
3	Get methods list	methods = type.GetMethods()	methods is array of MethodInfo objects for System.String
4	Get properties list	properties = type.GetProperties()	properties is array of PropertyInfo objects for System.String
5	Display method names	foreach method in methods	Print method.Name for each method
6	Display property names	foreach property in properties	Print property.Name for each property
7	End	No more actions	Program ends

💡 All methods and properties of the object's type have been inspected and displayed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
obj	null	"Hello"	"Hello"	"Hello"	"Hello"	"Hello"
type	null	null	System.String	System.String	System.String	System.String
methods	null	null	null	MethodInfo[]	MethodInfo[]	MethodInfo[]
properties	null	null	null	null	PropertyInfo[]	PropertyInfo[]

Key Moments - 3 Insights

Why do we call GetType() on the object before getting methods or properties?

GetType() returns the type information of the object, which is needed to access its methods and properties via reflection, as shown in step 2 of the execution_table.

Are methods and properties the same thing when inspecting a type?

No, methods are actions the object can perform, while properties are data values it holds. They are retrieved separately using GetMethods() and GetProperties(), as seen in steps 3 and 4.

Why do we get arrays of MethodInfo and PropertyInfo instead of the actual methods or properties?

Reflection returns metadata objects (MethodInfo, PropertyInfo) describing methods and properties, not the actual executable code or data. This allows inspection without invoking them, as shown in steps 3 and 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'type' after step 2?

A null

B "Hello"

C System.String

D MethodInfo[]

💡 Hint

Check the 'type' variable value in variable_tracker after step 2.

At which step do we get the list of properties of the object?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Action' column in execution_table for getting properties.

If we changed obj to an integer instead of a string, what would change in the execution?

A The type variable would be System.Int32 instead of System.String

B The methods array would be empty

C The properties array would be null

D The program would crash

💡 Hint

Consider what GetType() returns for different object types as shown in step 2.

Concept Snapshot

Inspecting methods and properties:
- Use obj.GetType() to get type info
- Use type.GetMethods() to get methods list
- Use type.GetProperties() to get properties list
- Methods and properties are metadata objects
- Useful for reflection and dynamic inspection

Full Transcript

This example shows how to inspect an object's methods and properties in C#. First, we create an object instance, here a string "Hello". Then we get its type information using GetType(). Next, we retrieve the list of methods with GetMethods() and the list of properties with GetProperties(). These return arrays of MethodInfo and PropertyInfo objects, which describe the methods and properties without executing them. We can then display their names or other details. This process is called reflection and helps us understand what an object can do or what data it holds at runtime.

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