C# CSOM - Check if File Exists in Document Library

Question

I'm coding in C# using CSOM, my app uploads a template asp.net page to the "/Pages/" library, I need it to check if a file exists in that location with the same name prior to file upload (then maybe it can return a bool value).

I did have a quick look but the majority of the solutions I found referred to the use of Javascript, or applied to on-prem deployments.

If someone could please point me in the right direction I would appreciate it.

Answer 1

You could consider the following approaches to determine whether file exists or not.

Query based

You could construct CAML query to find list item by its Url as demonstrated below:

public static bool FileExists(List list, string fileUrl)
{
    var ctx = list.Context;
    var qry = new CamlQuery();
    qry.ViewXml = string.Format("<View Scope=\"RecursiveAll\"><Query><Where><Eq><FieldRef Name=\"FileRef\"/><Value Type=\"Url\">{0}</Value></Eq></Where></Query></View>",fileUrl);
    var items = list.GetItems(qry);
    ctx.Load(items);
    ctx.ExecuteQuery();
    return items.Count > 0;
}

Usage

using (var ctx = GetSPOContext(webUri,userName,password))
{
     var list = ctx.Web.Lists.GetByTitle(listTitle);
     if(FileExists(list,"/documents/SharePoint User Guide.docx"))
     {
          //...
     }
}

Web.GetFileByServerRelativeUrl Method

Use Web.GetFileByServerRelativeUrl Method to return the file object located at the specified server-relative URL.

If file does not exists the exception Microsoft.SharePoint.Client.ServerException will be encountered:

  public static bool TryGetFileByServerRelativeUrl(Web web, string serverRelativeUrl,out Microsoft.SharePoint.Client.File file)
    {
        var ctx = web.Context;
        try{
            file = web.GetFileByServerRelativeUrl(serverRelativeUrl);
            ctx.Load(file);
            ctx.ExecuteQuery();
            return true;
        }
        catch(Microsoft.SharePoint.Client.ServerException ex){
            if (ex.ServerErrorTypeName == "System.IO.FileNotFoundException")
            {
                file = null;
                return false;
            }
            else
                throw;
        }
    }

Usage:

 using (var ctx = GetSPOContext(webUri,userName,password))
 {
      Microsoft.SharePoint.Client.File file;
      if(TryGetFileByServerRelativeUrl(ctx.Web,"/documents/SharePoint User Guide.docx",out file))
      {
          //...
      }
 }