Check if a datareader has rows or not in Asp.net

Question

My code:

string sqlQuery1 = "select * from employees where depid=6";
SqlDataReader Dr1 = dbconn.RunQueryReturnDataReader(sqlQuery1);

if(Dr1.read()) {    //or if (Dr1["empname"] != DBNull.Value)

            while (Dr1.Read())
            {        
                Label1.Text = Dr1["empname"].ToString();  
                Label2.Text = Dr1["empdes"].ToString(); 
                ...

            }
            Dr1.Close();
 }
 else {
            Label1.text = "defaultValue";
            Label2.text = "defaultValue";
            ...
 }

I just want to check SqlDataReader has no records to display. If no records ,the labels should showdefault values preassigned by me or If has record display datareader value on label. (Assume either SqlDataReader has 1 recode or has norecord only)

How can I check first datareader hasRow or not?

I have tried two ways as above code.

if(Dr1.read()) - this way working fine. But after execute If statement ,it has no value to display on labels , since read() will increase the pointer. As a result label1 ,Label2.. Nothing display.
if (Dr1["empname"] != DBNull.Value)

This way generate an exception when Sqldatareader has norows.

error: System.InvalidOperationException: Invalid attempt to read when no data is present

Please help me. tx

Ray Cheng · Accepted Answer · 2012-06-02 05:07:24Z

10

try...

if(Dr1.HasRows)
{
   //....
}

answered Jun 2, 2012 at 5:07

Ray Cheng

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1 Comment

Ray Cheng Over a year ago

Please remember to check for NULL like Nikhil D did.

Nikhil D · Accepted Answer · 2012-06-02 05:57:16Z

6

if (Dr1 == null || !Dr1.HasRows) {
    // Do something
}

answered Jun 2, 2012 at 5:57

Nikhil D

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4 Comments

devan Over a year ago

Tx for answer. Can you plz explain me difference between checking Dr1 and Dr1.HasRows.

Nikhil D Over a year ago

If Dr1==null is true, it will stop the evaluation - ||(OR) operator has no need to evaluate the right hand side of the expression if it knows the left hand side is true.

devan Over a year ago

no..you didn't get it. I asked ,what does it mean by (DataReader = null) and what is mean by (dataReader.HasRows = false) ? What is the dif between them?

Nikhil D Over a year ago

NULL just mean that you try to call Dr1 that is not initialized (null). And Hasrows means it is initialised but has no data(rows)

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