> For the complete documentation index, see [llms.txt](https://chsakell.gitbook.io/mongodb-csharp-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chsakell.gitbook.io/mongodb-csharp-docs/crud-basics/update-documents/operators.md).

# Operators

## *Set* operator - *$set*

The *$set* operator is used to update the value of a specified field. 

{% tabs %}
{% tab title="Syntax" %}

```csharp
Builders<T<.Update.Set(doc => doc.<field>, <value>)
```

{% endtab %}
{% endtabs %}

The sample updates the *FirstName* field of the first document in the collection.

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
            .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// create a Set operator update definition
var updateNameDefinition = Builders<User>.Update
            .Set(u => u.FirstName, "Chris");

// update the document
var updateNameResult = await collection
            .UpdateOneAsync(firstUserFilter, 
            updateNameDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

var bsonUpdateNameDefinition = Builders<BsonDocument>
            .Update.Set("firstName", "John");

var bsonUpdateNameResult = await bsonCollection
            .UpdateOneAsync(bsonFirstUserFilter, 
            bsonUpdateNameDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, 
	{ $set: { firstName: "Chris"  }});

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

### Multiple fields update

You can update multiple document's fields in one operation by declaring more than one update definitions.

The sample updates the first document's *Phone*, *Website* and *FavoriteSports (array field).*

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
        .GetCollection<User>(Constants.UsersCollection);

var multiUpdateDefinition = Builders<User>.Update
        .Set(u => u.Phone, "123-456-789")
        .Set(u => u.Website, "https://chsakell.com")
        .Set(u => u.FavoriteSports, 
                new List<string> { "Soccer", "Basketball" });

var multiUpdateResult = await collection
        .UpdateOneAsync(firstUserFilter, 
                multiUpdateDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

var bsonMultiUpdateDefinition = Builders<BsonDocument>.Update
    .Set("phone", "123-456-789")
    .Set("website", "https://chsakell.com")
    .Set("favoriteSports", 
        new List<string> { "Soccer", "Basketball" });

var bsonMultiUpdateResult = await bsonCollection
    .UpdateOneAsync(bsonFirstUserFilter, 
        bsonMultiUpdateDefinition);

```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { $set: { 
    phone: "123-456-789", 
    website: "https://chsakell.com", 
    favoriteSports: ["Soccer", "Basketball"]  
}});

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

## *Inc* operator - *$inc*

The *$inc* operator is used to increase the value of a specified field by a specified amount.&#x20;

```csharp
Builders<T<.Update.Inc(doc => doc.<field>, <value>)
```

The sample increments the first document's salary.

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
            .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// create an $inc update definition
var incrementSalaryDefinition = Builders<User>
            .Update.Inc(u => u.Salary, 450);
            
var incrementSalaryResult = await collection
            .UpdateOneAsync(firstUserFilter, 
                        incrementSalaryDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

var bsonIncrementSalaryDefinition = Builders<BsonDocument>
            .Update.Inc("salary", 450);
            
var bsonIncrementSalaryResult = await bsonCollection
      .UpdateOneAsync(bsonFirstUserFilter, 
         bsonIncrementSalaryDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { $inc: 
	{ salary: NumberDecimal("450.00") }});

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

{% hint style="success" %}
The $inc operator can be used with negative values to decrease a specified field's value
{% endhint %}

## *Min* operator - *$min*

The *$min* operator is used to update the value of a specified field **only if the new value is less than** the current value.

{% tabs %}
{% tab title="Syntax" %}

```csharp
Builders<T<.Update
    .Min(doc => doc.<field>, <value>)
```

{% endtab %}
{% endtabs %}

The sample decreases the first document's *salary* value from 3000 to 2000 :moneybag: .

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
    .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// preparation - set current salary to 3000
// for demo only
await collection.UpdateOneAsync(firstUserFilter, Builders<User>
    .Update.Set(u => u.Salary, 3000));
    
// update only if the new value is less than the current
var minUpdateDefinition = Builders<User>
    .Update.Min(u => u.Salary, 2000);
    
// 2000 is less than 3000 so update succeeds
var minUpdateResult = await collection
    .UpdateOneAsync(firstUserFilter, minUpdateDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

await bsonCollection.UpdateOneAsync(bsonFirstUserFilter,
    Builders<BsonDocument>.Update.Set("salary", 3000));

// would not update if the new salary was > 3000
var bsonMinUpdateDefinition = Builders<BsonDocument>
    .Update.Min("salary", 2000);
    
var bsonMinUpdateResult = await bsonCollection
    .UpdateOneAsync(bsonFirstUserFilter, 
        bsonMinUpdateDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { $min: { 
	salary: NumberDecimal("2000") } })


--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

{% hint style="info" %}
Of course if the new value is equal to the current one, the update result will return that no documents updated.

```javascript
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 0
}
```

{% endhint %}

## *Max* operator - *$max*

The *$max* operator is used to update the value of a specified field **only if the new value is greater than** the current value.

{% tabs %}
{% tab title="Syntax" %}

```csharp
Builders<T<.Update
    .Max(doc => doc.<field>, <value>)
```

{% endtab %}
{% endtabs %}

The sample increases the first document's *salary* value from 3000 to 3500 :moneybag: .

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
    .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// preparation - set current salary to 3000
// for demo only
await collection.UpdateOneAsync(firstUserFilter, Builders<User>
    .Update.Set(u => u.Salary, 3000));
    
// update only if the new value is greater than the current
var maxUpdateDefinition = Builders<User>
    .Update.Max(u => u.Salary, 3500);
    
// 3500 is greater than 3000 so update succeeds
var maxUpdateResult = await collection
    .UpdateOneAsync(firstUserFilter, maxUpdateDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

await bsonCollection.UpdateOneAsync(bsonFirstUserFilter,
    Builders<BsonDocument>.Update.Set("salary", 3000));

// would not update if the new salary was < 3500
var bsonMaxUpdateDefinition = Builders<BsonDocument>
    .Update.Max("salary", 3500);
    
var bsonMaxUpdateResult = await bsonCollection
        .UpdateOneAsync(bsonFirstUserFilter, 
            bsonMaxUpdateDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { $max: { 
		salary: NumberDecimal("3500") } 
})

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

## *Mul* operator - *$mul*

The *$mul* operator is used to multiply the current value of a specified field by a specified value.

{% tabs %}
{% tab title="Syntax" %}

```csharp
Builders<T<.Update.Mul(doc => doc.<field>, <value>)
```

{% endtab %}
{% endtabs %}

The sample doubles the first document's *salary* value from 1000 to 2000 using the $mul operator :moneybag: .

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
    .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// preparation - set current salary to 1000
// for demo only
await collection.UpdateOneAsync(firstUserFilter, 
    Builders<User>.Update.Set(u => u.Salary, 1000));
    
// multiply the current salary value by 2
var mulUpdateDefinition = Builders<User>
    .Update.Mul(u => u.Salary, 2);
    
var mulUpdateResult = await collection
    .UpdateOneAsync(firstUserFilter, mulUpdateDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
        .GetCollection<BsonDocument>(Constants.UsersCollection);

await bsonCollection.UpdateOneAsync(bsonFirstUserFilter,
    Builders<BsonDocument>.Update
        .Set("salary", 1000));

var bsonMulUpdateDefinition = Builders<BsonDocument>
    .Update.Mul("salary", 2);
    
var bsonMulUpdateResult = await bsonCollection
    .UpdateOneAsync(bsonFirstUserFilter, 
        bsonMulUpdateDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { $mul: { salary: 2 } })

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

## *Unset* operator - *$unset*

The *$unset* operator is used to remove a field from a document.

{% tabs %}
{% tab title="Syntax" %}

```csharp
Builders<T<.Update.Unset(doc => doc.<field>)
```

{% endtab %}
{% endtabs %}

The sample removes :x: the *Website* field from a user document.

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
    .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// remove the website field
var removeWebsiteDefinition = Builders<User>
    .Update.Unset(u => u.Website);

var removeWebsiteFieldUpdateResult = await collection
    .UpdateOneAsync(firstUserFilter, 
        removeWebsiteDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

var bsonRemoveWebsiteDefinition = Builders<BsonDocument>
            .Update.Unset("website");
            
var bsonRemoveWebsiteFieldUpdateResult =
    await bsonCollection.UpdateOneAsync(bsonFirstUserFilter, 
                bsonRemoveWebsiteDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { $unset: { website: ""  }})

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}

// user document

{
	"_id" : ObjectId("5e9d578781f29c3b1c22d796"),
	"gender" : 1,
	"firstName" : "Tracey",
	"lastName" : "Pfannerstill",
	"userName" : "Tracey_Pfannerstill97",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/mattlat/128.jpg",
	"email" : "Tracey_Pfannerstill99@yahoo.com",
	"dateOfBirth" : ISODate("1960-02-09T21:33:43.279+02:00"),
	"address" : {
		"street" : "636 Klein Corners",
		"suite" : "Apt. 556",
		"city" : "Kacieport",
		"state" : "New Mexico",
		"zipCode" : "58913-4315",
		"geo" : {
			"lat" : -48.7019,
			"lng" : -111.2376
		}
	},
	"phone" : "320-280-8093 x4487",
	"website" : "josh.com",
	"company" : {
		"name" : "Sawayn - Donnelly",
		"catchPhrase" : "Customer-focused mobile groupware",
		"bs" : "maximize cross-media e-tailers"
	},
	"salary" : 1716,
	"monthlyExpenses" : 2203,
	"favoriteSports" : [
		"Cricket",
		"Formula 1",
		"Table Tennis",
		"Water Polo",
		"Basketball",
		"Handball",
		"American Football"
	],
	"profession" : "Financial Adviser"
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

{% hint style="warning" %}

#### &#x20;​​ ⚡ Danger ​ ⚡​​ Danger ​ ⚡​​ Danger ​ ⚡

Use **caution** when applying the *Unset* operator!! In case you unset a *non nullable* property then you might end up having unexpected results. For example, if you unset the *salary* field on a user document, which is a decimal field, then the next time you read that document, the salary will be 0, not null!

```csharp
// remove salary field - decimal property
var removeSalaryDefinition = Builders<User>
    .Update.Unset(u => u.Salary);
    
var removeSalaryFieldUpdateResult =
    await collection.UpdateOneAsync(firstUserFilter, 
    removeSalaryDefinition);

// firstUser.Salary is equal to 0!
var firstUser = await collection.Find(firstUserFilter)
    .FirstOrDefaultAsync();
```

{% endhint %}

## *Rename* operator - *$rename*

The *$rename* operator is used to rename a field.&#x20;

{% tabs %}
{% tab title="Syntax" %}

```csharp
Builders<T<.Update
    .Rename(doc => doc.<field>, <new-name>)
```

{% endtab %}
{% endtabs %}

The sample updates the *Phone* field of the first document to *PhoneNumber* using the *$rename* operator.

{% tabs %}
{% tab title="C#" %}
{% code title="Update/BasicOperators.cs" %}

```csharp
var collection = database
    .GetCollection<User>(Constants.UsersCollection);

// create an empty filter
var firstUserFilter = Builders<User>.Filter.Empty;

// rename the phone field to phoneNumber for the first user
var renamePhoneDefinition = Builders<User>.
    Update.Rename(u => u.Phone, "phoneNumber");

// update the document
var renamePhoneFieldUpdateResult = await collection
    .UpdateOneAsync(firstUserFilter, 
        renamePhoneDefinition);
```

{% endcode %}
{% endtab %}

{% tab title="Bson" %}

```csharp
var bsonCollection = database
            .GetCollection<BsonDocument>(Constants.UsersCollection);

var bsonRenamePhoneDefinition = Builders<BsonDocument>
            .Update.Rename("phone", "phoneNumber");
            
var bsonRenamePhoneFieldUpdateResult = await bsonCollection
            .UpdateOneAsync(bsonFirstUserFilter, 
                        bsonRenamePhoneDefinition);
```

{% endtab %}

{% tab title="Shell" %}

```javascript
db.users.updateOne({}, { 
	$rename: { phone: "phoneNumber" } 
})

--------------------------- 
        
// sample update result
{
	"acknowledged" : true,
	"matchedCount" : 1,
	"modifiedCount" : 1
}
```

{% endtab %}

{% tab title="User" %}

```csharp
public class User
{
    [BsonId]
    [BsonIgnoreIfDefault] // required for replace documents 
    public ObjectId Id { get; set; }
    public Gender Gender { get; set; }
    public string FirstName {get; set; }
    public string LastName {get; set; }
    public string UserName {get; set; }
    public string Avatar {get; set; }
    public string Email {get; set; }
    public DateTime DateOfBirth {get; set; }
    public AddressCard Address {get; set; }
    public string Phone {get; set; }
    
    [BsonIgnoreIfDefault]
    public string Website {get; set; }
    public CompanyCard Company {get; set; }
    public decimal Salary { get; set; }
    public int MonthlyExpenses { get; set; }
    public List<string> FavoriteSports { get; set; }
    public string Profession { get; set; }
}
```

{% endtab %}
{% endtabs %}

{% hint style="warning" %}
When renaming document fields make sure the new field names can be matched back you your C# models. You can control the field's name in the database using th&#x65;**`[BsonElement]`** attribute. In the following example, the *Phone* property will be saved as *phoneNumber* in the database while can be deserialized back to the *Phone* property properly.

```csharp
[BsonElement("phoneNumber")]
public string Phone {get; set; }
```

{% endhint %}