[英]How to fix StreamWriter error “cannot implicitly convert type string to System.IO.StreamWriter”
我在 Visual Studio 2017 社區中使用 C#。
我有一個正在嘗試優化的工作、功能齊全的程序。 簡而言之,程序從文本文件中讀取文本和數字,進行一些數學運算和重新格式化,然后輸出到一個新的文本文件。
我要優化的部分是文本行寫入 output 文件的方式。 這是有效的:
using System.IO
// Let's start building the MA output text file now.
// Designate an output file --- put it in same directory as original files
// give MA file ame name as the original file -- but different extension.
maOutFile = dir + "\\" + serialNumber[f] + ".ma";
//Create MA header lines and write to file.
string maHeaderLine1 = "TITLE: S/N:" + serialNumber[f] + "\n";
string maHeaderLine2 = "ENGLISH(IN)/METRIC(MM) INDICATOR :IN-P\n";
// Open up the file for writing
File.WriteAllText(maOutFile, maHeaderLine1);
File.AppendAllText(maOutFile, maHeaderLine2);
上面的代碼工作正常。 我擔心它效率不高,尤其是在網絡速度較慢的情況下。 每次寫入文件時,它都會打開和關閉文件。
所以,為了讓它運行得更快,我想我會嘗試 StreamWriter。
我的 StreamWriter 代碼如下所示:
// Designate an output file --- put it in same directory as the original files
// give MA file same name as the original file -- with different extension.
// maOutFile = dir + "\\" + serialNumber[f] + ".ma";
StreamWriter outfile;
outfile = dir + "\\" + serialNumber[f] + ".ma";
//Create MA header lines and write to file.
string maHeaderLine1 = "TITLE: S/N:" + serialNumber[f] + "\n";
string maHeaderLine2 = "ENGLISH(IN)/METRIC(MM) INDICATOR :IN-P\n";
// Open up the file for writing
//File.WriteAllText(maOutFile, maHeaderLine1);
//File.AppendAllText(maOutFile, maHeaderLine2);
outfile.WriteLine(maHeaderLine1);
outfile.WriteLine(maHeaderLine2);
Visual Studio 不喜歡我使用 StreamWriter 的新代碼。 它在 "outfile = dir + "\" + serialNumber[f] + ".ma" 行中等號右側的所有內容下放置一條紅線;
當我 hover 將鼠標懸停在紅線代碼上時,消息是“無法將類型字符串隱式轉換為 System.IO.StreamWriter”。
我的新代碼有什么不喜歡的地方?
您將字符串變量分配給 StreamWriter object,而不是創建 StreamWriter object。
嘗試以下
using (StreamWriter sw = new StreamWriter(dir + "\\" + serialNumber[f] + ".ma"))
{
string maHeaderLine1 = "TITLE: S/N:" + serialNumber[f] + "\n";
string maHeaderLine2 = "ENGLISH(IN)/METRIC(MM) INDICATOR :IN-P\n";
// Open up the file for writing
//File.WriteAllText(maOutFile, maHeaderLine1);
sw.WriteLine(maHeaderLine1);
sw.WriteLine(maHeaderLine2);
}
您正在嘗試在此處將字符串分配給 StreamWriter:
outfile = dir + "\\" + serialNumber[f] + ".ma";
並查看您嘗試將文件打開為 stream 的代碼,類似於:
string outFileDir = dir + "\\" + serialNumber[f] + ".ma";
StreamWriter outFile = new StreamWriter(outFileDir);
string fileName = dir + "\\" + serialNumber[f] + ".ma" ;
try
{
using (StreamWriter writer = new StreamWriter(fileName))
{
string maHeaderLine1 = "TITLE: S/N:" + serialNumber[f] + "\n";
string maHeaderLine2 = "ENGLISH(IN)/METRIC(MM) INDICATOR :IN-P\n";
writer.Write(maHeaderLine1 + maHeaderLine2);
}
}
catch(Exception exp)
{
Console.Write(exp.Message);
}
}
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