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sql to linq in c# code

Posted on 2014-01-25
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Last Modified: 2016-02-10
cn.Open();
            SqlCommand cmsql;
            SqlDataReader drsql;


            string sql = "select max(patientid)as patientid from patient";



            cmsql = new SqlCommand(sql, cn);

            drsql = cmsql.ExecuteReader();
            if (drsql.Read())
            {
         
                    int pid = Convert.ToInt16(drsql["patientid"].ToString()) + 1;
                    txtpatientid.Text = pid.ToString();
                

            }


            else
            {

                txtpatientid.Text = "1";
            }
            cn.Close();
            cmsql.Dispose();
            drsql.Close();
       

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this is my sql code how i make it in linq


my table name is== patient
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Question by:loveuajay
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6 Comments
 
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Expert Comment

by:Habib Pourfard
ID: 39808691
using (MyDataContext dc = new MyDataContext())
{
    int pid = dc.patients.Max(t => t.patientid);
}

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Accepted Solution

by:
Fernando Soto earned 500 total points
ID: 39808754
Hi loveuajay;

The following code snippet will do the same as your SQL code in the question.

// Create a Linq to SQL DataContext 
var db = new DataContextType();
Int16 maxPatientId = 0;

// Get the max ID from the patient table 
if( db.patient.Count() != 0 )
    maxPatientId = (Int16) db.patient.Max( p => p.patientid );

txtpatientid.Text = (++maxPatientId).ToString();

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0
 

Author Comment

by:loveuajay
ID: 39809691
i get this error

Error      1      The type or namespace name 'DataContextType' could not be found (are you missing a using directive or an assembly reference?)      D:\ajay\jolly tech project\jollytech p1\jollytech p1\patient.cs      79      26      jollytech p1
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LVL 62

Expert Comment

by:Fernando Soto
ID: 39810106
Hi loveuajay;

When working with Linq to SQL the first thing you need to do is create your data context and in Linq to SQL it is creating a EDMX which is Object Relational/Model, This model defines the tables in the database and the relationships between them. I would suggest reading the following web link which describe what LinQ to SQL is and how to create the OR/M, EDMX file and querying the database.

Using Linq to SQL Part 1

Once you have created the EDMX file which maps the database to the classes in your code that is what you will use for the variable DataContextType in the code snippet I posted.
0
 

Author Closing Comment

by:loveuajay
ID: 39811550
thanks i get it
0
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 39812068
Not a problem, glad to help.
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