How do I replace the input of a raw txt file with user inputted text inside a textbox

See more:

C#

WPF

MVVM

Binding

I have a dll file that for now uses a .txt file as input that is located in the debug folder of my application. I want to replace this .txt file with text as submitted inside of a textbox within my application.

I'm still new to MVVM and WPF, and managed to get the dll functions working. I am however struggling with replacing the .txt file with textbox input. If anyone could help me out or point me towards the right path that would be greatly appreciated.
For clarification I want the method to read Textdetail (the text inside the textbox) instead of the contents of the file.


Method and string names have been changed as I cant share too much.

Inside the class

public string Textdetail { get; set; }

            [DllImport("Blabla.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
    
            public static extern void Method1 (
                string string1,
                StringBuilder string2,
                StringBuilder string3);
    
            public static void Createtxt(object data, string fileName)
            {
                var stream = new FileStream(fileName, FileMode.OpenOrCreate);
                using (StreamWriter writer = new StreamWriter(stream, Encoding.UTF8))
                {
                    writer.Write(data);
                    writer.Close();
                }
            }
            public static void ExecuteProject()
            {
                string file = "Dependendfile.txt";
                int capacity = 1000000;
                int maxCapacity = 999999999;
                StringBuilder string1 = new StringBuilder(capacity, maxCapacity);
                StringBuilder string2 = new StringBuilder(capacity, maxCapacity);
                LogixConvertRungs(File.ReadAllText(file), string1, string2);
                CreateTxt(string1.ToString(), "File1-" + "Demo"+ ".txt");
                CreateTxt(string1.ToString(), "File2-" + "Demo"+ ".txt");
            }

the xaml textbox text

<TextBox x:Name="txt_replacefilewithtextfromthis" 
                 TextWrapping="Wrap" 
                 AcceptsReturn="True"
                 FontFamily="Corsiva" 
                 FontSize="11"
                 Text="{Binding Textdetail, Mode=TwoWay}"/>

What I have tried:

I've tried looking up multiple tutorials, but cant figure out how to do it. The application either ignores the textbox input or gives off different erros