How to put information from the database into an intptr

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C#

SQL-Server

I know my question may be funny. I use this function to identify registered fingerprint in database and this function is for the fingerprint sensor of "zkteco" company. This function is like this:

[Function]
  public static int DBIdentify(IntPtr dbHandle, byte[] temp, ref int fid, ref int score)
[Purpose]
  This function is used to conduct 1:N comparison.
[Parameter Description]
 dbHandle
  Cache handle
temp
  Template used for comparison
fid
  Returned fingerprint ID
score
  Returned comparison score
[Return Value]
  0 Succeeded
  Others Failed (See the error code description.)

My problem is with this IntPtr dbHandle.
Please let me explain more, I am going to use this method to identify the fingerprint registered in the database, but I don't know how to put my database information in this temporary variable IntPtr dbHandle.

What I have tried:

I get the registered fingerprint string from my database with this:

int ret = zkfp.ZKFP_ERR_OK;
string RegTemplate;
int fid = 0, score = 0;
 foreach (DataGridViewRow item in dataGridView1.Rows)
 {
  try
    {

    RegTemplate = item.Cells[0].Value.ToString();
    byte[] FinalRegTemplate = zkfp2.Base64ToBlob(RegTemplate);
    ret = zkfp2.DBIdentify(mDBHandle, FinalRegTemplate, ref fid, ref score);
      }
     catch
        {}

Quote:

And my problem is with the first parameter of the "DBIdentify" function.
Because the first parameter does not accept string

and I want to give it to the IntPtr dbHandle, but the variable does not accept the string and I don't know how to convert it and put it in this function:

public static int DBIdentify(IntPtr dbHandle, byte[] temp, ref int fid, ref int score)