using UnityEngine;
using System.Collections;
using System;
using System.Runtime.InteropServices;

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
public class OpenFileName
{
public int structSize = 0;
public IntPtr dlgOwner = IntPtr.Zero;
public IntPtr instance = IntPtr.Zero;
public String filter = null;
public String customFilter = null;
public int maxCustFilter = 0;
public int filterIndex = 0;
public String file = null;
public int maxFile = 0;
public String fileTitle = null;
public int maxFileTitle = 0;
public String initialDir = null;
public String title = null;
public int flags = 0;
public short fileOffset = 0;
public short fileExtension = 0;
public String defExt = null;
public IntPtr custData = IntPtr.Zero;
public IntPtr hook = IntPtr.Zero;
public String templateName = null;
public IntPtr reservedPtr = IntPtr.Zero;
public int reservedInt = 0;
public int flagsEx = 0;
}

public class LocalDialog
{
//鏈接指定系統函數 打開文件對話框
[DllImport("Comdlg32.dll", SetLastError = true, ThrowOnUnmappableChar = true, CharSet = CharSet.Auto)]
public static extern bool GetOpenFileName([In, Out] OpenFileName ofn);
public static bool GetOFN([In, Out] OpenFileName ofn)
{
return GetOpenFileName(ofn);
}

//鏈接指定系統函數 另存為對話框
[DllImport("Comdlg32.dll", SetLastError = true, ThrowOnUnmappableChar = true, CharSet = CharSet.Auto)]
public static extern bool GetSaveFileName([In, Out] OpenFileName ofn);
public static bool GetSFN([In,Out] OpenFileName ofn)
{
return GetSaveFileName(ofn);
}
}

using UnityEngine;
using System.Collections;
using System.Runtime.InteropServices;
public class DialogTest : MonoBehaviour {
void OnGUI()
{
if (GUI.Button(new Rect(10,10,100,50),"Open"))
{
OpenFileName openFileName = new OpenFileName();
openFileName.structSize = Marshal.SizeOf(openFileName);
openFileName.filter = "Excel文件(*.xlsx)\0*.xlsx";
openFileName.file = new string(new char[256]);
openFileName.maxFile = openFileName.file.Length;
openFileName.fileTitle = new string(new char[64]);
openFileName.maxFileTitle = openFileName.fileTitle.Length;
openFileName.initialDir = Application.streamingAssetsPath.Replace(‘/‘,‘\\‘);//默認路徑
openFileName.title = "窗口標題";
openFileName.flags = 0x00080000 | 0x00001000 | 0x00000800 | 0x00000008;

if (LocalDialog.GetSaveFileName(openFileName))
{
Debug.Log(openFileName.file);
Debug.Log(openFileName.fileTitle);
}
}
}
}

Unity調用系統窗口選擇文件或文件路徑