Add new data to table (ASP.NET Web API)

I have ASP.NET Web API project.

I this project I have table

Here is table syntax:

CREATE TABLE [dbo].[TimeTable] (
[Id]         INT            IDENTITY (1, 1) NOT NULL,
[Company]    NVARCHAR (MAX) NULL,
[INN]        NVARCHAR (MAX) NULL,
[StartDay]   NVARCHAR (MAX) NULL,
[StartPause] NVARCHAR (MAX) NULL,
[EndDay]     NVARCHAR (MAX) NULL,
[EndPause]   NVARCHAR (MAX) NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)

);

And here is class:

 public partial class TimeTable
{
    public int Id { get; set; }
    public string Company { get; set; }
    public string INN { get; set; }
    public string StartDay { get; set; }
    public string StartPause { get; set; }
    public string EndDay { get; set; }
    public string EndPause { get; set; }
}

App will send in first request Company, INN and StartDay data. In second Company, 'INN' and StartPause data.

First I need to check if company and inn exists, if not write data to table.

I can do this like this

public IHttpActionResult PostTimeTable(TimeTable timeTable)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }



        db.TimeTables.Add(timeTable);
        db.SaveChanges();

        return CreatedAtRoute("DefaultApi", new { id = timeTable.Id }, timeTable);
    }

But if data exists I need to select row with Company = timeTable.Company and INN = time.Table.INN

I try to it Like here for Company first

.Where(x=>x.Company = timeTable.Company)

But I have error

Severity Code Description Project File Line Suppression State Error CS0029 Cannot implicitly convert type 'string' to 'bool' trackingappbackend C:\Users\nemes\Documents\Visual Studio 2017\Projects\trackingappbackend\trackingappbackend\Controllers\StartPausesController.cs 84 Active

How I can do this?