How do I bind the local variable values to the datagrid in WPF MVVM project

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MVVM

Inside the method am getting the values in one local variable(when i click button method will run and get values in local variable).how do i bind the local variable values to datagrid

What I have tried:

ViewModel :

code is :

local variable(UserDetails)

  private void Show()
        {
            //Users.AddRange(_context.Users);

           var UserDetails = (from a in _context.DocumentDatas
                               join b in _context.MetaDatas on a.DocId equals b.MId



                               select new
                               {
                                   a.Id,
                                   a.DocomentName,
                                   a.DocumentPath,
                                   b.Properties,
                                   b.Values



                               }).ToList();

Created one property

private ObservableCollection<userdetails> _UserDetails;

        public ObservableCollection<userdetails> UserDetails
        {
            get { return _UserDetails; }
            set
            {
                _UserDetails = value;
                OnpropertyChanged("UserDetails");

            }
        }

XAML

and databinding :

<datagrid grid.row="5" grid.column="3" grid.columnspan="3" margin="20" horizontalalignment="Center" verticalalignment="Center" width="350" 
="" itemssource="{Binding UserDetails}" autogeneratecolumns="False">
            <datagrid.columns>
                <datagridtextcolumn header="Id" binding="{Binding Id,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
                <datagridtextcolumn header="DocomentName" binding="{Binding DocomentName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
                <datagridtextcolumn header="DocumentPath" binding="{Binding DocumentPath,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
                <datagridtextcolumn header="Properties" binding="{Binding Properties,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
                <datagridtextcolumn header="Values" binding="{Binding Values,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">