# CSV

## Read

Perigee ships with several powerful CSV tools that make reading even complicated CSV's very easy and fast with memory efficient span based data reads.

```csharp
//Get a memory stream to the file
using MemoryStream ms = new MemoryStream(File.ReadAllBytes("Products.csv"));

//Read the CSV as a list of T classes
List<Product> products = CSVReader.ReadAs<Product>(ms);

//Read the csv as a DataTable
DataTable ProductTable =  CSVReader.ToDataTable(ms, out var res);
```

{% hint style="info" %}
When using the `.ToDataTable()` methods, you get the resulting parse parameters sent back as an out variable. This allows you to check it's encoding, formatting, delimiters, header row location, etc.&#x20;
{% endhint %}

## Write

To write CSV data supply a `DataTable` and any additional handlers to override specifics on a data type.

* We'll read in the `Products.CSV` as our source.
* Let's then declare a writer, and set it to `BAR` delimited
* Register a decimal handler that write's any decimals with 3 digits after the period
  * The handler sends you back the **object** (in this case a decimal)
  * The **Row Index**.
  * The **Column Name**.
  * It expects a return value of the string converted version, as well as a `boolean` indicating if the transform was successful.
  * Any NON-SUCCESSFUL transformed handlers are added to the writers **LoadLog** property and can be viewed after conversion.
* Then simply call `.Write()`.

```csharp
//Read products CSV from above reader demo
using MemoryStream ms = new MemoryStream(File.ReadAllBytes("Products.csv"));
DataTable ProductTable = CSVReader.ToDataTable(ms, out var res);

//Write this table back out to CSV using a custom decimal format and BAR delimited
CSVWriter writer = new CSVWriter(ProductTable, (d) => "Products").WithDelimiter("|");

//You can register booleans, strings, datetimes, decimals... etc.
writer.RegisterHandler<decimal>((dec, rowIndex, colName) => new Tuple<string, bool>(dec.ToString("N3"), true));    

//Write it out
string content = writer.Write();
```

{% code title="writerResult.csv" %}

```csharp
Products
ID|PRODUCT|PRICE
1|MILK|8.990
2|55-INCH TV|899.990
3|BREAD|1.990
```

{% endcode %}

## Clean

Maybe the only thing you need to do is take the absolutely horrendous CSV data in the [Sample Data section](#sample-data) and just create a CSV that can be cleanly loaded into another system.

```csharp
using MemoryStream ms = new MemoryStream(File.ReadAllBytes("Products.csv"));

string cleanContent = CSVReader.Clean(ms);
```

This transforms the very badly formatted CSV Sample Data into this:

```csv
ID,PRODUCT,PRICE
1,MILK,8.99
2,55-INCH TV @ aisle 4,899.99
3,BREAD,1.99
```

### Sample Data

Included is the sample data and classes used above.

{% code title="Products.csv" %}

```csv
CSVData as of 1/1/2001
By: Yours Truly
ID@PRODUCT@PRICE
1@MILK@8.99
2@'55-INCH TV @ aisle 4'@899.99
3@BREAD@1.99
```

{% endcode %}

```csharp
public class Product
{
    public int id { get; set; } = 0;
    public string product { get; set; }
    public decimal price { get; set; }
}
```


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