C import Xls data method summary I (upload files and create Workbooks)

C# Import .xls Data method summary I （ Upload files and create workbooks ）

Preface ：
The software used is VS2019
The reference used is ：NPOI.dll
NPOI Is built on POI 3.x A program above version ,NPOI Can be installed without Office In the case of Word or Excel The document is read and written .NPOI It's an open source C# Reading and writing Excel、WORD Wait for Microsoft OLE2 Items for component documents .

One 、 Receive uploaded files

About C# The uploaded files are basically used HttpPostedFileBase To receive the uploaded data
Used as a base class of some kind , The former provides access to a single file that has been uploaded by the client .

HttpPostedFileBase() Class has the following private methods that can be used , Are related to the uploaded files later

1. ContentLength
   When overridden in a derived class , Get the size of the uploaded file （ In bytes ）.
2. ContentType
   When overridden in a derived class , Get uploaded files MIME Content type .
3. FileName
   The name of the file on the client , Include directory path .
4. InputStream
   When overridden in a derived class , Get the System.IO.Stream object , To prepare to read the contents of the file .
5. SaveAs
   When overridden in a derived class , Save the contents of the uploaded file .

Two 、 Judge whether the uploaded file conforms to .xls file

Idea of batch import data ：
1、 Get the read file -> Determine if the data type is correct ;
2、 Convert files to binary arrays ;
3、 Convert binary array into memory stream ;
4、 utilize NPOI Read the data in the memory stream into Excel

1、 Get the path of the uploaded file

Top entry required ： using System.IO;

// Get file suffix 
string fileExtension = Path.GetExtension(excelFile.FileName);

2、 adopt Equals() Determine whether the file type conforms to

Equals() Express ： Determines whether this instance is associated with another specified System.String Object has the same value .
return true or false

// Judge whether the document is excel form 
if (".xls".Equals(fileExtension.ToLower()) || ".xlsx".Equals(fileExtension.ToLower())){
    
}else{
    
}

3、 Declare a binary array to store the uploaded file

The maximum length of the array is the length of the uploaded file

// Declare the binary array to store the file 
byte[] fileBytes = new byte[excelFile.ContentLength];

4、 Convert the uploaded file into a binary array and assign the previous variable

The length of the binary array is the size of the uploaded file , By receiving the uploaded file .ContentLength Can get
The first parameter is the binary array written , The second parameter is the write location , The third is the length written

// Convert the file into binary data group and store it in fileBytes
excelFile.InputStream.Read(fileBytes, 0, excelFile.ContentLength);

5、 Convert binary arrays into memory streams

 // Convert binary array into memory stream 
MemoryStream excelFileStream = new MemoryStream(fileBytes);

6、 Convert memory stream to workbooks

// Convert memory stream to workbooks 
IWorkbook workbook = new HSSFWorkbook(excelFileStream);

7、 The complete first part of the code

 public ActionResult ImportExcel(HttpPostedFileBase excelFile){
    
 	ReturnJson returnJson = new ReturnJson(); //  Put back the entity class data created 
	int saveCount = 0;
    //  Idea of batch import data 
    // 1、 Get the read file -> Determine if the data type is correct ;
    // 2、 Convert files to binary arrays ;
    // 3、 Convert binary array into memory stream ;
    // 4、 utilize NPOI Read the data in the memory stream into Excel
    try{
    
    	// Get file suffix 
        string fileExtension = Path.GetExtension(excelFile.FileName);
        // Judge whether the document is excel form 
        if (".xls".Equals(fileExtension.ToLower()) || ".xlsx".Equals(fileExtension.ToLower())){
    
        	// Declare the binary array to store the file 
            byte[] fileBytes = new byte[excelFile.ContentLength];
            // Convert the file into binary data group and store it in fileBytes
            excelFile.InputStream.Read(fileBytes, 0, excelFile.ContentLength);
            // Convert binary array into memory stream 
            MemoryStream excelFileStream = new MemoryStream(fileBytes);
            // Convert memory stream to workbooks 
            IWorkbook workbook = new HSSFWorkbook(excelFileStream);
 			// Determine if there are worksheets in the workbook 
            if (workbook.NumberOfSheets > 0){
    
            	//  Continue to the next step and write the next article 
            }else{
    
            	returnJson.Text = " There are no worksheets in the workbook , Please check ！";
            }
        }else{
    
	        returnJson.Text = " Wrong file type Uploaded , Please check ！";
        }
	}catch (Exception e)
    {
    
        Console.WriteLine(e);
        returnJson.Text = " Data exception ："+e;
    }
    return Json(returnJson, JsonRequestBehavior.AllowGet);
}