如何在C#中导入CSV到数据表

What is a CSV File?

A CSV file (Comma Separated Values file) is a type of plain text file that uses specific structuring to arrange tabular data. It's a common format for data interchange as CSV is simple, compact, and works with numerous platforms. In a CSV file, data is separated by commas, and each new line signifies a new row, with the column headers often present in the first row.

Understanding DataTables in C#

A DataTable is part of the ADO.NET library in C# and represents a single table of in-memory data. It comprises rows and columns, and each column can be of a different data type. DataTables are highly flexible and can represent data in a structured format, making them ideal for handling CSV file data.

Step 1: Create a New C# Project

1. Open Visual Studio.
2. Select File > New > Project.
3. Choose a C# Console or Windows Forms application, and name it appropriately.

Step 2: Install IronXL

IronXL is a powerful library that allows you to work with Excel and CSV files in C#. To use it, you need to install it via NuGet Package Manager. In Visual Studio:

1. Go to Tools > NuGet Package Manager > Manage NuGet Packages for Solution.

2. Search for IronXL.Excel.

   

3. Install the package to your project.

Step 1: Set Up Your Environment

using IronXL;
using System.Data;

using IronXL;
using System.Data;

Imports IronXL
Imports System.Data

These using statements include the necessary namespaces for our task.

Step 2: Create a Method to Import CSV

Define a class, CsvToDataTable, with a static method ImportCsvToDataTable. This method will be responsible for converting the CSV file into a DataTable.

public class CsvToDataTable
{
    public static DataTable ImportCsvToDataTable(string filePath)
    {
        // Code snippet to import CSV will be placed here
        return null; // Placeholder return statement
    }
}

public class CsvToDataTable
{
    public static DataTable ImportCsvToDataTable(string filePath)
    {
        // Code snippet to import CSV will be placed here
        return null; // Placeholder return statement
    }
}

Public Class CsvToDataTable
	Public Shared Function ImportCsvToDataTable(ByVal filePath As String) As DataTable
		' Code snippet to import CSV will be placed here
		Return Nothing ' Placeholder return statement
	End Function
End Class

Step 3: Load the CSV File

Inside the ImportCsvToDataTable method, start by loading the CSV file. IronXL provides a straightforward way to do this:

// Load the CSV file
WorkBook workbook = WorkBook.LoadCSV(filePath);

// Load the CSV file
WorkBook workbook = WorkBook.LoadCSV(filePath);

' Load the CSV file
Dim workbook As WorkBook = WorkBook.LoadCSV(filePath)

WorkBook.LoadCSV is a method in IronXL to load CSV files. Here, filePath is the path to your CSV file.

Step 4: Convert CSV to DataTable

Convert the loaded CSV data into a DataTable. This step is crucial as it transforms the data into a format that can be easily manipulated and displayed within a C# application.

// Get the first worksheet
WorkSheet sheet = workbook.DefaultWorkSheet;
// Convert CSV worksheet to DataTable
DataTable dataTable = sheet.ToDataTable();
return dataTable;

// Get the first worksheet
WorkSheet sheet = workbook.DefaultWorkSheet;
// Convert CSV worksheet to DataTable
DataTable dataTable = sheet.ToDataTable();
return dataTable;

' Get the first worksheet
Dim sheet As WorkSheet = workbook.DefaultWorkSheet
' Convert CSV worksheet to DataTable
Dim dataTable As DataTable = sheet.ToDataTable()
Return dataTable

This snippet converts the CSV data into a DataTable. DefaultWorkSheet fetches the first worksheet from the workbook, equivalent to the entire CSV data in the case of a CSV file. The ToDataTable method is a powerful feature of IronXL that efficiently maps the CSV data to a DataTable structure, including a column header row if present in the first row of the CSV file.

Step 5: Utilize the Method in Your Application

Now, use the ImportCsvToDataTable method in your application. For instance, you might want to call this method when the application starts or when the user uploads a CSV file.

// Usage
string csvFilePath = "csvfile.csv";
DataTable dataTable = CsvToDataTable.ImportCsvToDataTable(csvFilePath);

// Usage
string csvFilePath = "csvfile.csv";
DataTable dataTable = CsvToDataTable.ImportCsvToDataTable(csvFilePath);

' Usage
Dim csvFilePath As String = "csvfile.csv"
Dim dataTable As DataTable = CsvToDataTable.ImportCsvToDataTable(csvFilePath)

This code snippet demonstrates how to call the ImportCsvToDataTable method. Replace "csvfile.csv" with the actual file path of your CSV file.

Step 6: Working with the Output DataTable

foreach (DataRow row in dataTable.Rows)
{
    foreach (var item in row.ItemArray)
    {
        Console.Write($"{item} ");
    }
    Console.WriteLine();
}

foreach (DataRow row in dataTable.Rows)
{
    foreach (var item in row.ItemArray)
    {
        Console.Write($"{item} ");
    }
    Console.WriteLine();
}

For Each row As DataRow In dataTable.Rows
	For Each item In row.ItemArray
		Console.Write($"{item} ")
	Next item
	Console.WriteLine()
Next row

var filteredRows = dataTable.AsEnumerable()
                            .Where(row => row.Field<string>("ColumnName") == "SomeValue");

var filteredRows = dataTable.AsEnumerable()
                            .Where(row => row.Field<string>("ColumnName") == "SomeValue");

Dim filteredRows = dataTable.AsEnumerable().Where(Function(row) row.Field(Of String)("ColumnName") = "SomeValue")

Output Of Code

Once you run the code, it'll load the CSV file and import its data to the DataTable. After that, it'll show the contents of the DataTable columns in the console. It helps to verify that the data is correctly imported into the DataTable.

Handling a Different Delimiter

Commas are the default delimiter in CSV files. However, CSV files may not always use commas to separate values. Sometimes, a semicolon, tab, or other characters are used as delimiters. To handle this in IronXL:

Specifying a Custom Delimiter: Before loading the CSV file, you can specify your file's delimiter. For example, if your file uses a semicolon (;), you can set it like this:

WorkBook workbook = WorkBook.LoadCSV(filePath, listDelimiter: ";");

WorkBook workbook = WorkBook.LoadCSV(filePath, listDelimiter: ";");

Dim workbook As WorkBook = WorkBook.LoadCSV(filePath, listDelimiter:= ";")

Handling Large CSV Files

When dealing with large CSV files, it's important to consider memory usage and performance. IronXL provides efficient ways to handle large files without loading the entire file into memory at once. You can read the file in chunks or utilize streaming APIs provided by IronXL to manage memory usage effectively.