C# – datatable not accepting the value of varbinary

asp.netcdatabasedatatablesql server

the value buf has a datatype varbinary(max) and the value is 0x0000002D

string buF =
    "0x" + BitConverter.ToString((byte[])dt.Rows[i]["BuF"]).Replace("-", "");
    Label3.Text = buF;

i use the value to find the fileid

DataTable dt = new DataTable();
        SqlConnection connection = new SqlConnection();
        connection.ConnectionString = ConfigurationManager.ConnectionStrings["XYZ"].ConnectionString;
        connection.Open();
        SqlCommand sqlCmd = new SqlCommand("SELECT FileID FROM Backed where MachineID = @machineID  AND BuF =@buF", connection);
        SqlDataAdapter sqlDa = new SqlDataAdapter(sqlCmd);
        sqlCmd.Parameters.AddWithValue("machineID", strID);
        sqlCmd.Parameters.AddWithValue("buF", buF);
        sqlDa.Fill(dt);
        connection.Close();

i does not use the value of buf and i dont get the correct filid….

but if i use this with the value0x0000002D instead of buf i get the file id… why is this happening… i tried everything but nothing seems to work

i need help

Best Answer

The equivalent type for varbinary in C# is byte[], not string. Also, as Hogan said, AddWithValue tries to assume a data type. Instead, you can make it explicit:

sqlCmd.Parameters.Add("buF", SqlDbType.VarBinary, -1).Value = yourByteArray;

The -1 for length corresponds to varbinary(max).

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – LINQ query on a DataTable

You can't query against the DataTable's Rows collection, since DataRowCollection doesn't implement IEnumerable<T>. You need to use the AsEnumerable() extension for DataTable. Like so:

var results = from myRow in myDataTable.AsEnumerable()
where myRow.Field<int>("RowNo") == 1
select myRow;

And as @Keith says, you'll need to add a reference to System.Data.DataSetExtensions

AsEnumerable() returns IEnumerable<DataRow>. If you need to convert IEnumerable<DataRow> to a DataTable, use the CopyToDataTable() extension.

Below is query with Lambda Expression,

var result = myDataTable
    .AsEnumerable()
    .Where(myRow => myRow.Field<int>("RowNo") == 1);

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – LINQ query on a DataTable

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