Entity Framework - Simplified by Mohd Manzoor Ahmed - HTML preview

Chapter 3: Exploring Entity Data Model

 In this chapter we are going to explore the class that gets generated whenever we

create Entity Data Model

 The class is OrganizationModel.Designer.cs and I’ll double click this file.

 Now, there are two important things that you need to remember from this file

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Entity Framework - Simplified

1. Namespace (You got namespace as OrganizationModel)

namespace OrganizationModel {}

o Hope you might have remembered when we were creating Entity Data Model,

In the wizard we gave the name of the model as OrganizationModel.

o So “OrganizationModel” is the namespace.

o On the page wherever you need to access the data with the help of Entity

Data Model, You need to say Using OrganizationModel; i.e., you need to add

this namespace on the page wherever you code.

2. The Object contexts that we have that is OrganizationEntities

o You need to create the context object whenever you want to work with Entity

Data Model.

o So, this class is present in the OrganizationModel namespace that’s why we

need to add this namespace and create the object of this class.

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Entity Framework - Simplified

 Let us see the entities that got created for each table.

 So, we should have 2 entities. Entities are nothing but the objects – the classes.

o public partial class tbl_Dept : EntityObject

o public partial class tbl_Emp : EntityObject

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 So, I’ve got one entity that is Department tbl_Dept and the other entity that is

tbl_Emp and they contains the properties Did(Department ID) which is of type

int, (DName) Department name, HOD and Gender for tbl_Dept.

public global::System.Int32 Did

{

get

{

return _Did;

}

set

{

if (_Did != value)

{

OnDidChanging(value);

ReportPropertyChanging("Did");

_Did = StructuralObject.SetValidValue(value);

ReportPropertyChanged("Did");

OnDidChanged();

}

}

}

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public global::System.String Dname

{

get

{

return _Dname;

}

set

{

OnDnameChanging(value);

ReportPropertyChanging("Dname");

_Dname = StructuralObject.SetValidValue(value, true);

ReportPropertyChanged("Dname");

OnDnameChanged();

}

}

public global::System.String HOD

{

get

{

return _HOD;

}

set

{

OnHODChanging(value);

ReportPropertyChanging("HOD");

_HOD = StructuralObject.SetValidValue(value, false);

ReportPropertyChanged("HOD");

OnHODChanged();

}

}

 It also contains one extra property that is nothing but the Navigation property

that means we say whenever there is a primary and foreign key relationship it is

creating a property that is called as Navigation property.

 From department table we can move to Employee table with the help of

Navigation property called as tbl_Emp.

public EntityCol ection<tbl_Emp> tbl_Emp

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{

get

{

return

((IEntityWithRelationships)this).RelationshipManager.Get RelatedCollection<tbl_Emp>("

OrganizationModel.FK_tbl_Emp_tbl_Dept", "tbl_Emp");

}

set

{

if ((value != nul ))

{

((IEntityWithRelationships)this).RelationshipManager.InitializeRelatedCollection

<tbl_Emp>("OrganizationModel.FK_tbl_Emp_tbl_Dept", "tbl_Emp", value);

}

}

}

public global::System.Int32 Eid

{

get

{

return _Eid;

}

set

{

if (_Eid != value)

{

OnEidChanging(value);

ReportPropertyChanging("Eid");

_Eid = StructuralObject.SetValidValue(value);

ReportPropertyChanged("Eid");

OnEidChanged();

}

}

}

public global::System.String EName

{

get

{

return _EName;

}

set

{

OnENameChanging(value);

ReportPropertyChanging("EName");

_EName = StructuralObject.SetValidValue(value, false);

ReportPropertyChanged("EName");

OnENameChanged();

}

}

public global::System.Double ESal

{

get

{

return _ESal;

}

set

{

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Entity Framework - Simplified

OnESalChanging(value);

ReportPropertyChanging("ESal");

_ESal = StructuralObject.SetValidValue(value);

ReportPropertyChanged("ESal");

OnESalChanged();

}

}

public global::System.String EGen

{

get

{

return _EGen;

}

set

{

OnEGenChanging(value);

ReportPropertyChanging("EGen");

_EGen = StructuralObject.SetValidValue(value, false);

ReportPropertyChanged("EGen");

OnEGenChanged();

}

}

public global::System.DateTime EDOB

{

get

{

return _EDOB;

}

set

{

OnEDOBChanging(value);

ReportPropertyChanging("EDOB");

_EDOB = StructuralObject.SetValidValue(value);

ReportPropertyChanged("EDOB");

OnEDOBChanged();

}

}

public Nul able<global::System.Int32> Did

{

get

{

return _Did;

}

set

{

OnDidChanging(value);

ReportPropertyChanging("Did");

_Did = StructuralObject.SetValidValue(value);

ReportPropertyChanged("Did");

OnDidChanged();

}

}

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public EntityReference<tbl_Dept > tbl_DeptReference

{

get

{

return

((IEntityWithRelationships)this).RelationshipManager.Get RelatedReference<tbl_Dept >("

OrganizationModel.FK_tbl_Emp_tbl_Dept", "tbl_Dept");

}

set

{

if ((value != nul ))

{

((IEntityWithRelationships)this).RelationshipManager.InitializeRelatedRefer

ence<tbl_Dept>("OrganizationModel.FK_tbl_Emp_tbl_Dept ", "tbl_Dept",

value);

}

}

}

 Anyway we are going to see how to use all these things in our future chapters.

So, these are the entities that get created.

 Now, operations on these entities are available in this class OrganizationEntities.

 So, you have a class which is partial and you have partial methods and you have

objectset properties.

 And, the important thing is AddToMethods.

 So, AddTotbl_Dept is the method to insert some record into the department

table.

 AddTotble_Emp is the method used to insert some record into the Employee table

public void AddTotbl_Dept(tbl_Dept tbl_Dept)

{

base.AddObject("tbl_Dept", tbl_Dept);

}

public void AddTotbl_Emp(tbl_Emp tbl_Emp)

{

base.AddObject("tbl_Emp", tbl_Emp);

}

public partial class OrganizationEntities : ObjectContext

 Now, one important thing is OrganizationEntities class is partial because there

are many cases where you need to edit this class that means before insertion,

before adding this to the database, I want to perform some business operations

or business validations.

 I can go and write the code here itself. But, the problem is that whenever I

refresh my OrganizationModel or if I add some new tables to this model or if I

update the model if I perform anything on the model it is going to regenerate this

file means it’ll override all our code.

 So, in those scenarios what is that we can do is we can have a separate class

which is again a partial class and you can add your customized code there.

 So, that whenever you update Entity Data Model you code should not get

overridden.

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Entity Framework - Simplified

Chapter 4: Exploring Entity Data Model in EF 5.X

 There are two ways of working with Entity Framework i.e., ObjectContext and

DbContext.

 This book deals with ObjectContext.

 Now, if at all you are working on Visual Studio 2012 with latest version of Entity

Framework 5.X.

 Here are few settings that you need to perform once once you generate your Entity

Data Model or you can say your edmx file to work with ObjectContext.

 So, you need to perform two steps.

 Right click in edmx file go for properties and say Code Generation Strategy to

Default.

 In your OrganizationModel hierarchy you’ll find two files with .tt extension

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Entity Framework - Simplified

 Simply delete those files.

 Now, you can rebuild the project and you’ll see that everything is successful.

 Go for OrganizationDBEntities1 file.

 And you’ll find all the things as usual.

 These are the two steps that you need to perform if at all you want to work with

Entity Framework on Visual Studio 2012.

 Now, what are these tt files, how can we work with tt files? All these things we can

see in our next release.

 So, in our next Chapters we will see basic operations i.e., performing insert, update,

delete and read operations from Entity Data Model.

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Entity Framework - Simplified

Chapter 5 : Performing an Insert Operation

 In this chapter I am going to show you how to perform the insert operation on Entity

Data Model that is in your Entity Framework.

 It is very simple. Say, I’ve a form it is a normal ASP.NET form that I’ve created to

insert data into the department table.

 As we know that department id is auto generated column we do not require a field

for it on the form.

<table cel padding="0" cel spacing="0" class="style1">

<tr>

<td style="text-align: right">

Dept ID</td>

<td>

<asp:TextBox ID="txt Did" runat="server"></asp:TextBox>

</td>

</tr>

<tr>

<td style="text-align: right">

&nbsp;</td>

<td>

<asp:Button ID="btnSearch" runat="server" onclick="btnSearch_Click"

Text="Search" />

</td>

</tr>

<tr>

<td style="text-align: right">

Dept Name</td>

<td>

<asp:TextBox ID="txt DName" runat="server"></asp:TextBox>

</td>

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</tr>

<tr>

<td style="text-align: right">

HOD</td>

<td>

<asp:TextBox ID="txtHOD" runat="server"></asp:Text Box>

</td>

</tr>

<tr>

<td style="text-align: right">

Gender</td>

<td>

<asp:RadioButtonList ID="rblGender" runat="server" RepeatDirection="Horizontal">

<asp:ListItem Value="M">Male</asp:ListItem>

<asp:ListItem Value="F">Female</asp:ListItem>

</asp:RadioButtonList >

</td>

</tr>

<tr>

<td style="text-align: right">

IsActive</td>

<td>

<asp:CheckBox ID="ckbActive" runat="server" />

</td>

</tr>

<tr>

<td style="text-align: right">

<asp:Button ID="btnCancel" runat="server" Text="Cancel" />

</td>

<td>

<asp:Button ID="btnSave" runat="server" OnClick="btnSave_Click" Text="Save" />

<asp:Button ID="btnUpdate" runat="server" onclick="btnUpdate_Click"

Text="Update" />

<asp:Button ID="btnDelete" runat="server" onclick="btnDelete_Click"

Text="Delete" />

</td>

</tr>

<tr>

<td colspan="2" style="text-align: center">

<asp:GridView ID="grdDept" runat="server" CellPadding="4" ForeColor="#333333"

GridLines="None">

<AlternatingRowStyle BackColor="White" ForeColor="#284775" />

<EditRowStyle BackColor="#999999" />

<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />

<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />

<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />

<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />

<SelectedRowStyle BackColor="#E2DED6" Font -Bold="True" ForeColor="#333333" />

<SortedAscendingCel Style BackColor="#E9E7E2" />

<SortedAscendingHeaderStyle BackColor="#506C8C" />

<SortedDescendingCel Style BackColor="#FFFDF8" />

<SortedDescendingHeaderStyle BackColor="#6F8DAE" />

</asp:GridView>

</td>

</tr>

</table>

 Next, department name I’ve created a textbox for this for HOD I’ve a textbox, for

gender I’ve a radio button list and for Active flag I’ve IsActive checkbox.

 Now, on this save button click I need this data to get inserted into this department

table.

 I’ll double click the save button and write code.

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 As we learnt in our previous chapter if you want to perform anything on Entity Data

Model you need to use a namespace that is nothing but using OrganizationModel;

that we’ve in our solution explorer In Organization Model.

 This is the namespace that we add OrganizationModel. And I’ll create an object of

this class that is OrganizationEntities.

OrganizationEntities OE = new OrganizationEntities();

 Now I want to perform an insert operation on Department table that means I need to

create the object for tbl_Dept

protected void btnSave_Click(object sender, EventArgs e)

{

OrganizationEntities OE = new OrganizationEntities();

// This is the entity that we got the entity for department table

tbl_Dept d = new tbl_Dept();

//Department ID is auto increment I need not to do anything for this

//HOD Name, txtDName, txtHOD these are al the ID’s of the textboxes that we’ve on the form

d.Dname = txtDName.Text.ToString();

d.HOD = txtHOD.Text.ToString();

d.Gender = rblGender.SelectedValue.ToString();

//This is of type BooleanWhenever the checkbox is checked I should set it to true else to false

d.Active = ckbActive.Checked;

//Now department object is ready. I need to insert this department d in the department table. So, I’l

//perform that operation with the help of OrganizationEntities object

OE.AddTotbl_Dept(d);

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//Final y save changes. It is going to reflect in the database.