sql to linq in c# code

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
loveuajayAsked:
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Fernando SotoConnect With a Mentor RetiredCommented:
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
 
Habib PourfardSoftware DeveloperCommented:
using (MyDataContext dc = new MyDataContext())
{
    int pid = dc.patients.Max(t => t.patientid);
}

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loveuajayAuthor Commented:
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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Fernando SotoRetiredCommented:
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.
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loveuajayAuthor Commented:
thanks i get it
0
 
Fernando SotoRetiredCommented:
Not a problem, glad to help.
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