Unity 实用教程 之 调用系统窗口选择文件或路径-百度经验 (baidu.com)

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public class OpenSelectFileName
    {
        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
    {
        //链接指定系统函数       打开文件对话框
        [DllImport("Comdlg32.dll", SetLastError = true, ThrowOnUnmappableChar = true, CharSet = CharSet.Auto)]
        public static extern bool GetOpenFileName([In, Out] OpenSelectFileName ofn);
        public static bool GetOFN([In, Out] OpenSelectFileName ofn)
        {
            return GetOpenFileName(ofn);
        }

        //链接指定系统函数        另存为对话框
        [DllImport("Comdlg32.dll", SetLastError = true, ThrowOnUnmappableChar = true, CharSet = CharSet.Auto)]
        public static extern bool GetSaveFileName([In, Out] OpenSelectFileName ofn);
        public static bool GetSFN([In, Out] OpenSelectFileName ofn)
        {
            return GetSaveFileName(ofn);
        }
    }//Class_end


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('/', '\\');//默认路径
            openFileName.title = "窗口标题";
            openFileName.flags = 0x00080000 | 0x00001000 | 0x00000800 | 0x00000008;
            if (LocalDialog.GetOpenFileName(openFileName))
            {
                Debug.Log(openFileName.file);
                Debug.Log(openFileName.fileTitle);
            }
        }
    }
}

1,关于openFileName.filter = "Excel文件(.xlsx)\0.xlsx";的注意事项：\0在字符串中代表字符串截止，即对于\0后的字符不进行处理，需要选择多个格式时，使用“\0\0”包围后缀不进行显示，如：

openFileName.filter = "Excel文件(*.xlsx)\0*.xlsx\0Word文件(*.doc)\0*.doc\0";

后缀结尾处不加“\0”似乎会出现乱码