Method that checks whether to disable or enable the buttons depending on whether data is null or not
In looking at your method, you have a lot of repetition in building your two dictionaries before composing your final result. If you were to simply regroup your code to separate the building of your first and second dictionaries, and the data that supports the construction, you would produce the following method: 

[OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
public ActionResult CheckButtons()
{
    int planId = (int)UserSession.GetValue(StateNameEnum.ID, "PlanID");

    planning resultSetA = db.planning.Where(t =&gt; t.PlanId == planId).Join(db.matching_image, p =&gt; p.MatchingImageId, i =&gt; i.Id,
        (p, i) =&gt; new
        {
            planning = p,
            i.View
        }).Where(j =&gt; j.View == "A").Select(j =&gt; j.planning).FirstOrDefault();

    structure sA = db.structure.FirstOrDefault(s =&gt; s.PlanId == planId &amp;&amp; s.Type == "A");

    Dictionary&lt;string, string&gt; buttonADictionary = new Dictionary&lt;string, string&gt;();
    buttonADictionary.Add("C", resultSetA.CorrespondingId != null ? "disabled" : "enabled");
    buttonADictionary.Add("R", resultSetA.ResponseId != null ? "disabled" : "enabled");
    buttonADictionary.Add("S", (sA != null &amp;&amp; sA.Point_x != null) ? "disabled" : "enabled");
    buttonADictionary.Add("D", resultSetA.DistalId != null ? "disabled" : "enabled");
    buttonADictionary.Add("P", resultSetA.ProximalId != null ? "disabled" : "enabled");
    bool aHasData = buttonADictionary.ContainsValue("disabled");

    planning resultSetB = db.planning.Where(t =&gt; t.PlanId == planId).Join(db.matching_image, p =&gt; p.MatchingImageId, i =&gt; i.Id,
        (p, i) =&gt; new
        {
            planning = p,
            i.View
        }).Where(j =&gt; j.View == "B").Select(j =&gt; j.planning).FirstOrDefault();

    structure sB = db.structure.FirstOrDefault(s =&gt; s.PlanId == planId &amp;&amp; s.Type == "B");

    Dictionary&lt;string, string&gt; buttonBDictionary = new Dictionary&lt;string, string&gt;();
    buttonBDictionary.Add("C", resultSetB.CorrespondingId != null ? "disabled" : "enabled");
    buttonBDictionary.Add("R", resultSetB.ResponseId != null ? "disabled" : "enabled");
    buttonBDictionary.Add("S", (sB != null &amp;&amp; sB.Point_x != null) ? "disabled" : "enabled");
    buttonBDictionary.Add("D", resultSetB.DistalId != null ? "disabled" : "enabled");
    buttonBDictionary.Add("P", resultSetB.ProximalId != null ? "disabled" : "enabled");
    bool bHasData = buttonBDictionary.ContainsValue("disabled");

    return Json(new { buttonADictionary, buttonBDictionary, aHasData, bHasData }, JsonRequestBehavior.AllowGet);
}


It's evident at this point that your code at the top and at the bottom is effectively identical, only differing on a value passed into two queries and then on variable names. Inside this single method, you are violating the DRY principle: don't repeat yourself. So let's make the first extraction and create the method here: 

private Dictionary&lt;string, string&gt; GetButtonDictionary(int planId, string value)
{
    planning resultSet = db.planning.Where(t =&gt; t.PlanId == planId).Join(db.matching_image, p =&gt; p.MatchingImageId, i =&gt; i.Id,
        (p, i) =&gt; new
        {
            planning = p,
            i.View
        }).Where(j =&gt; j.View == value).Select(j =&gt; j.planning).FirstOrDefault();

    structure st = db.structure.FirstOrDefault(s =&gt; s.PlanId == planId &amp;&amp; s.Type == value);

    Dictionary&lt;string, string&gt; buttonDictionary = new Dictionary&lt;string, string&gt;();
    buttonDictionary.Add("C", resultSet.CorrespondingId != null ? "disabled" : "enabled");
    buttonDictionary.Add("R", resultSet.ResponseId != null ? "disabled" : "enabled");
    buttonDictionary.Add("S", (st != null &amp;&amp; st.Point_x != null) ? "disabled" : "enabled");
    buttonDictionary.Add("D", resultSet.DistalId != null ? "disabled" : "enabled");
    buttonDictionary.Add("P", resultSet.ProximalId != null ? "disabled" : "enabled");
    return buttonDictionary;
}


The method above takes two parameters: a planId that you have obtained, as well as a value. This second variable probably isn't a great name, but you have overloaded the meaning of your string in your original method (it's used to compare against a View property and a Type property) such that I couldn't immediately think of a better name. If you can think of one, just sub it in. 

With this extraction, it cleans up your original method nicely, because it can be cleaned up to the following: 

[OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
public ActionResult CheckButtons()
{
    int planId = (int)UserSession.GetValue(StateNameEnum.ID, "PlanID");
    Dictionary&lt;string, string&gt; buttonADictionary = GetButtonDictionary(planId, "A");
    Dictionary&lt;string, string&gt; buttonBDictionary = GetButtonDictionary(planId, "B");

    bool aHasData = buttonADictionary.ContainsValue("disabled");
    bool bHasData = buttonBDictionary.ContainsValue("disabled");

    return Json(new { buttonADictionary, buttonBDictionary, aHasData, bHasData }, JsonRequestBehavior.AllowGet);
}


Could we clean this up a little more? Possibly, but it's simplified enough for now so let's go back to the method we extracted. It has a couple of database queries that should probably individually be their own methods (SRP - Single Responsibility Principle), so let's go ahead and do that.

private Dictionary&lt;string, string&gt; GetButtonDictionary(int planId, string value)
{
    planning resultSet = GetPlanningResultSet(planId, value);
    structure st = GetStructure(planId, value);

    Dictionary&lt;string, string&gt; buttonDictionary = new Dictionary&lt;string, string&gt;();
    buttonDictionary.Add("C", resultSet.CorrespondingId != null ? "disabled" : "enabled");
    buttonDictionary.Add("R", resultSet.ResponseId != null ? "disabled" : "enabled");
    buttonDictionary.Add("S", (st != null &amp;&amp; st.Point_x != null) ? "disabled" : "enabled");
    buttonDictionary.Add("D", resultSet.DistalId != null ? "disabled" : "enabled");
    buttonDictionary.Add("P", resultSet.ProximalId != null ? "disabled" : "enabled");
    return buttonDictionary;
}

private planning GetPlanningResultSet(int planId, string value)
{
    planning resultSet = db.planning.Where(t =&gt; t.PlanId == planId).Join(db.matching_image, p =&gt; p.MatchingImageId, i =&gt; i.Id,
        (p, i) =&gt; new
        {
            planning = p,
            i.View
        }).Where(j =&gt; j.View == value).Select(j =&gt; j.planning).FirstOrDefault();
    return resultSet;
}

private structure GetStructure(int planId, string value)
{
   return db.structure.FirstOrDefault(s =&gt; s.PlanId == planId &amp;&amp; s.Type == value);
}


After doing this, you have the obvious bit of repetition left where you get your enabled settings where you repeat your null checks. So let's extract a method to deal with that.

private Dictionary&lt;string, string&gt; GetButtonDictionary(int planId, string value)
{
    planning resultSet = GetPlanningResultSet(planId, value);
    structure st = GetStructure(planId, value);

    Dictionary&lt;string, string&gt; buttonDictionary = new Dictionary&lt;string, string&gt;();
    buttonDictionary.Add("C", GetEnabledSetting(resultSet.CorrespondingId));
    buttonDictionary.Add("R", GetEnabledSetting(resultSet.ResponseId));
    buttonDictionary.Add("S", GetEnabledSetting(st != null ? st.Point_x : null));
    buttonDictionary.Add("D", GetEnabledSetting(resultSet.DistalId));
    buttonDictionary.Add("P", GetEnabledSetting(resultSet.ProximalId));
    return buttonDictionary;
}

private string GetEnabledSetting(object value)
{
    return value != null ? "disabled" : "enabled";
}


After we have completed this extraction, the full code now looks like the following: 

[OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
public ActionResult CheckButtons()
{
    int planId = (int)UserSession.GetValue(StateNameEnum.ID, "PlanID");
    Dictionary&lt;string, string&gt; buttonADictionary = GetButtonDictionary(planId, "A");
    Dictionary&lt;string, string&gt; buttonBDictionary = GetButtonDictionary(planId, "B");

    bool aHasData = buttonADictionary.ContainsValue("disabled");
    bool bHasData = buttonBDictionary.ContainsValue("disabled");

    return Json(new { buttonADictionary, buttonBDictionary, aHasData, bHasData }, JsonRequestBehavior.AllowGet);
}

private Dictionary&lt;string, string&gt; GetButtonDictionary(int planId, string value)
{
    planning resultSet = GetPlanningResultSet(planId, value);
    structure st = GetStructure(planId, value);

    Dictionary&lt;string, string&gt; buttonDictionary = new Dictionary&lt;string, string&gt;();
    buttonDictionary.Add("C", GetEnabledSetting(resultSet.CorrespondingId));
    buttonDictionary.Add("R", GetEnabledSetting(resultSet.ResponseId));
    buttonDictionary.Add("S", GetEnabledSetting(st != null ? st.Point_x : null));
    buttonDictionary.Add("D", GetEnabledSetting(resultSet.DistalId));
    buttonDictionary.Add("P", GetEnabledSetting(resultSet.ProximalId));
    return buttonDictionary;
}

private planning GetPlanningResultSet(int planId, string value)
{
    planning resultSet = db.planning.Where(t =&gt; t.PlanId == planId).Join(db.matching_image, p =&gt; p.MatchingImageId, i =&gt; i.Id,
        (p, i) =&gt; new
        {
            planning = p,
            i.View
        }).Where(j =&gt; j.View == value).Select(j =&gt; j.planning).FirstOrDefault();
    return resultSet;
}

private structure GetStructure(int planId, string value)
{
   return db.structure.FirstOrDefault(s =&gt; s.PlanId == planId &amp;&amp; s.Type == value);
}

private string GetEnabledSetting(object value)
{
    return value != null ? "disabled" : "enabled";
}


This is enough contribution for me. I'll leave it up to you to possibly create better variable names and get the code into a bit better compliance with C# standards. For example, you seem to have classes starting in lowercase (planning, structure) and those should start with capital letters. You seem to have DbSets that should be plural (and capitalized). Finally, this seems to be a lot of work to be in a controller, perhaps it could be be further extracted to a pure business layer. Those modifications would, of course, be up to you.