(VB.NET) curl with Variable Substitution in a GraphQL Request Body

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This example shows how to use variables inside a graphql request body using the {{variable_name}} syntax. When the HTTP request’s Content-Type indicates graphql, Chilkat automatically applies proper escaping to each substituted value, ensuring the resulting graphql remains valid.

Note: This example requires Chilkat v11.5.0 or greater.

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Dim success As Boolean = False

success = False

' Variable names are enclosed between {{ and }}
' Important: Variables should be placed inside the quotes.

' curl -X POST https://api.example.com/graphql \
'   -H "Content-Type: application/graphql; charset=utf-8" \
'   -H "Accept: application/json" \
'   --data-binary "mutation {
'   createUser(
'     input: {
'       name: \"{{name}}\"
'       city: \"{{city}}\"
'       note: \"{{note}}\"
'       bio: \"{{bio}}\"
'     }
'   ) {
'     id
'     name
'   }
' }"

' Build the above curl command.
Dim sbCurl As New Chilkat.StringBuilder
sbCurl.AppendLn("curl -X POST https://api.example.com/graphql \")
sbCurl.AppendLn("  -H ""Content-Type: application/graphql; charset=utf-8"" \")
sbCurl.AppendLn("  -H ""Accept: application/json"" \")
sbCurl.AppendLn("  -d ""mutation {")
sbCurl.AppendLn("  createUser(")
sbCurl.AppendLn("    input: {")
sbCurl.AppendLn("      name: \""{{name}}\""")
sbCurl.AppendLn("      city: \""{{city}}\""")
sbCurl.AppendLn("      note: \""{{note}}\""")
sbCurl.AppendLn("      bio: \""{{bio}}\""")
sbCurl.AppendLn("    }")
sbCurl.AppendLn("  ) {")
sbCurl.AppendLn("    id")
sbCurl.AppendLn("    name")
sbCurl.AppendLn("  }")
sbCurl.AppendLn("}""")

Dim curl As New Chilkat.HttpCurl

' Provide values for variables
curl.SetVar("name","José O'Connor")
curl.SetVar("city","München")
curl.SetVar("note","He said ""Hello, world!"" — and left…")
curl.SetVar("bio","Loves sushi, café visits, and π ≈ 3.14159")

' To demonstrate how the variables are replaced, this example does not execute the curl command. 
' Instead, it generates the raw HTTP request that would be sent if the curl command were run.
Dim sbRawRequest As New Chilkat.StringBuilder
success = curl.ToRawRequest(sbCurl.GetAsString(),sbRawRequest)
If (success = False) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


Debug.WriteLine(sbRawRequest.GetAsString())

' The output is shown below.
' Notice the quote chars around "Hello, world!" are properly escaped.

' POST /graphql HTTP/1.1
' Accept: application/json
' Host: api.example.com
' Content-Type: application/graphql; charset=utf-8
' Content-Length: 250
' 
' mutation {
'   createUser(
'     input: {
'       name: "José O'Connor"
'       city: "München"
'       note: "He said \"Hello, world!\" — and left…"
'       bio: "Loves sushi, café visits, and π ≈ 3.14159"
'     }
'   ) {
'     id
'     name
'   }
' }