Class with methods to retrieve data with Linq to sql

I think here is something wrong with code. I use a class with methods to get tenants from DB:

    public List<CrmTenant> GetAllTenants()
    {
        List<CrmTenant> tenantsList = new List<CrmTenant>();

        try
        {
            var crmTenants =
                 from tenant in context.CrmTenant
                 select tenant;

            if (crmTenants != null)
            {
                foreach (var tenant in crmTenants)
                {
                    tenantsList.Add(tenant);
                }
            }

            return tenantsList;
        }
        catch (Exception ex)
        {
            this.logger.Write("Failed to get all tenants from database.", "Exceptions", TraceEventType.Error, ex);
            return null;
        }
    }

    /// <summary>
    /// Gets Tenant by name.
    /// </summary>
    /// <returns></returns>
    public CrmTenant GetTenantByName(string tenantName)
    {
        CrmTenant crmTenant = null;

        try
        {
            crmTenant =
                 (from customerCrm in context.CrmTenant
                  where customerCrm.TenantName == tenantName
                  select customerCrm).Single();
            return crmTenant;
        }
        catch (Exception ex)
        {
            this.logger.Write(String.Format("Failed to get tenant '{0}' from database.", tenantName), "Exceptions", TraceEventType.Error, ex);
            return null;
        }
    }

    /// <summary>
    /// Gets tenant by Username.
    /// </summary>
    /// <returns></returns>
    public CrmTenant GetTenantByUserName(string userName)
    {
        CrmTenant crmTenant = null;

        try
        {
            crmTenant =
                 (from customerCrm in context.CrmTenant
                  where customerCrm.Username == userName
                  select customerCrm).Single();
            return crmTenant;
        }
        catch (Exception ex)
        {
            this.logger.Write(String.Format("Failed to get tenant by username '{0}' from database.", userName), "Exceptions", TraceEventType.Error, ex);
            return null;
        }
    }

Here is call for methods

// get tenant
var crmTenant = CrmServiceHandlerFactory.GetInstance().Resolve<TenantManager>().GetTenantByUserName(userName);

I am new in programming, could you please help me to improve this code