# Update

## Overview

MongoDB provides a set of update operators to help you update values on your collections' documents. This section contains several samples showing how to use these operators to update:

* Top level fields
* Embedded fields
* Array fields 

{% hint style="warning" %}
Complex update operations such as updating embedded fields, adding or removing items in embedded array fields might be straight forward when building the queries in the *Shell* but not so much when using the MongoDB C# driver
{% endhint %}

The section contains samples for the following operators:

| Operator   | Description                                                                          |
| ---------- | ------------------------------------------------------------------------------------ |
| **Set**    | Sets the value of a field in a document                                              |
| **Inc**    | Increments a field's value                                                           |
| **Min**    | Updates a field's value only if the specified value is **less** than the existing    |
| **Max**    | Updates a field's value only if the specified value is **greater** than the existing |
| **Mul**    | Multiplies a field's value by a specified amount                                     |
| **Unset**  | Removes the specified field from the document                                        |
| **Rename** | Renames a field                                                                      |

Other than the update operations there are also samples showing how to **replace** documents and **array** fields.

![](/files/-M53ClGU8vt-7gjtqyi_)

## Update Definition Builder :muscle: 

To create update operations using the MongoDB C# driver you need to create one or more **update definitions**. The syntax to create an update definition is the following:

> **Syntax**: `Builders<T>.Update.<Operator>(<field>,<value>)`

{% hint style="success" %}
:mage: An update definition can be the result of more than 1 update definitions on the same document which means you can build a query that updates multiple fields using different operators.

Here's' an example:&#x20;

> ```csharp
> var multiUpdateDefinition = Builders<User>.Update
>     .Set(u => u.Phone, "123-456-789") // update 1
>     .Inc(u => u.Salary, 300) // update 2
>     .Set(u => u.FavoriteSports, 
>         new List<string> 
>         { "Soccer", "Basketball" }); // update 3
> ```

{% endhint %}

## UpdateOne & UpdateMany

To update one or more documents use the **`UpdateOne`** and **`UpdateMany`** `IMongoCollection<T>` respectively.

> **Syntax**: `IMongoCollection<T>.UpdateOne(<filter>,<update-definition>)`

> **Syntax**: `IMongoCollection<T>.UpdateMany(<filter>,<update-definition>)`

{% hint style="success" %}
Update methods return information :information\_source:regarding total documents matched by the filter, total documents modified and if there was acknowledgement

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

{% endhint %}


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