using MathNet.Symbolics;
using System;
using System.IO;
using System.Text;private string ConvertToLatex(string mathExpression)
{return mathExpression.Replace(" * ", "").Replace("*", "");
}// 将函数定义为字符串
string functionString = "10 * x^2";
// 将函数解析为符号表达式
SymbolicExpression function = SymbolicExpression.Parse(functionString);
// 关于x符号化的微分函数
SymbolicExpression derivative = function.Differentiate("x"); 
// 代入x = -1到微分函数
SymbolicExpression x = SymbolicExpression.Parse("x");
int value = -1;
SymbolicExpression val1 = SymbolicExpression.Parse(value.ToString());
SymbolicExpression result = derivative.Substitute(x, val1);
string latexExpr0 =  ConvertToLatex(functionString);
string latexExpr1 = ConvertToLatex(derivative.ToString()); 
// 将求解结果函数和值写入Tex文件
string filePath = "derivative_value.tex"; // 文件路径
StringBuilder sb = new StringBuilder(500);string latexHead = @"\documentclass{article}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage{CJKutf8}
\begin{document}\begin{CJK}{UTF8}{gkai}%正文放在此行下与\end{CJK}之间就行
";
sb.Append(latexHead);
sb.Append("\r\n");
sb.Append("    设$f(x)="+ latexExpr0 + $"$，试按定义求 $f'({value})$。\r\n");
sb.Append("\r\n");
sb.Append("    解：$f'(x)="+ latexExpr1 + "$\r\n"); 
sb.Append("\r\n");
sb.Append($"    $f'({value})="+ result.ToString() + "$。\r\n"); 
string latexTail = @"
\end{CJK}
\end{document}
";
sb.Append(latexTail);string content = sb.ToString(); // 要写入的文本内容
Encoding utf8bom = new UTF8Encoding(true);
File.WriteAllText(filePath, content, utf8bom); 

derivative_value.tex文件内容：

\documentclass{article}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage{CJKutf8}
\begin{document}\begin{CJK}{UTF8}{gkai}%正文放在此行下与\end{CJK}之间就行设$f(x)=10x^2$，试按定义求 $f'(-1)$。解：$f'(x)=20x$$f'(-1)=-20$。\end{CJK}
\end{document}